I often have potential customers trying to weigh whether they need a zero turn vs a tractor.
Tractor means different things to different people. On the lower end they may mean a lawn tractor for $1000, on the upper end they mean a real tractor with a 3 point hitch, four wheel drive and a front end loader for $25,000. Of course there is much middle ground between those two extremes. I will try to cover a variety of pro's and con's to consider.
Flexibility / One machine serving multiple purposes: I think we can all appreciate having one tool that can do lots of things. For example, a 35hp 4wd diesel tractor with front end loader, backhoe attachment, belly mower and a few common 3 point hitch implements may sound like the ultimate machine, as it should be for $30,000. But even if $30,000 was within your budget it may be that a less expensive combination of equipment could serve your needs even better. The belly mower attachment alone is probably going to cost $4000-$5000, and even a $3000 zero turn would probably be more than twice as productive mowing grass. The backhoe attachment for many people is the several thousand dollar item that never gets used because it's too much trouble to take on and off. Perhaps instead of being prepared and waiting for the job to come along that needs a backhoe, just wait until that job comes along and rent a bigger better backhoe that fits the job for a fraction of the price of owing your own. Or if you would use the backhoe regularly, then it may stay on the tractor all the time in which case you may end up not using 3-point hitch implements because it's too much hassle to get the backhoe out of the way.
The reality for most rural home owners I speak to is that most of their time spent on outdoor equipment is consumed cutting grass, with second place usually going to maintaining a gravel driveway. If that be the case then having a multi-purpose solution that is weak at cutting grass is not a good solution.
I once sold a 52" zero turn to a customer to mow his yard, because his New Holland tractor with an 84" finish mower was too awkward to use in the yard. A year or so later, I asked him how it was working out. He said "great, but I feel like I'm wearing it out". He continued to say "When I get behind in mowing my pastures with my 84" finish mower, I use the 52" zero turn to catch up". When it comes to productivity and cut quality you just can't beat a zero turn.
As for scraping a drive way with a tractor, a 3 point hitch scrape blade on the back of a tractor is much more useful than a front bucket. That's not to say front buckets are not useful, they certainly are, but not so much for the drive way. If you are going to have a front bucket (front end loader) then you really need four wheel drive because when there is a heavy load in the front, the rear wheels will not have much traction. But if you don't need a front end loader then 2 wheel drive is completely sufficient for 3 point hitch implements such as a bush hog, scrape blade or box blade which attach to the rear of the tractor. Used 2 wheel drive 3 point hitch tractors can be purchased for a small fraction of the cost of four wheel drive tractors with loaders. You can probably find a nice used machine in the neighborhood of $5000. That combined with a $5000 zero turn would nicely take care of the yard, the pasture and the drive way a whole lot better than the $30,000 machine described above and with little or no time consuming switching of attachments.
Don't misunderstand me to be saying backhoes and front end loaders are not useful. They most certainly are. I personally have a dedicated (cannot be removed) backhoe, as well as a 4wd tractor, which has a front bucket but 90% of the time I have a grapple installed in place of the bucket because it gets much more use. Also a 2wd tractor with 3 point hitch. But my 60" zero turn mower still gets 10 times the hours of all the other equipment combined. For that reason, having highly productive mowing equipment is the best money spent among the pieces of equipment I own.
Will a zero turn do well in fields: If by fields you mean rough terrain with deep trenches, stumps and rocks, then no, a zero turn is not recommended. But if the ground underneath is relatively smooth and it is a field because it is not often mowed, then yes a zero turn is likely a good choice.
Inferior goods: There's a fill in the blank saying you may have heard adapted to different things that goes like this: "There are two kinds of people, those who have a zero turn mower and those who want a zero turn mower ." When filling the blank with "zero turn mower" it's actually holds true most of the time, to the point that that the "riding lawn tractor" market has become overwhelmingly what economists call an "inferior good". In other words most lawn tractor customers buy a lawn tractor in lieu of a zero turn because of price even though they would prefer to have a zero turn.
Economies of scale: This term simply means that with more quantity of an item being produced comes more efficiency or savings to lower the item's cost. At one time consumer zero turn mowers were not main stream at all and for that reason very expensive. Today, consumer grade Zero turns are very much mainstream and are mass produced making them an excellent value. The same is true of riding lawn tractors in the $1000-$2000 price range. But as you start to climb above that $2000 price point riding lawn tractors are not near as main stream as they used to be. If you look at the general build quality of materials and components used on a $3000 zero turn, you will find that a traditional front engine rider of similar materials and components will be much more expensive than the zero turn.
A well made front engine steering wheel rider: Because of what is explained in the two paragraphs above "Inferior Goods" and "Economies of scale", the quality riding tractor market has become much smaller with fewer choices and much more expensive. The unique customer that would still find this product to be their best option is a market minority and now pays a premium for a product that is no longer mainstream. Two of the biggest players in this market are Kubota and John Deere (not the ones at big box stores like Home Depot and Lowes).
Mainstream inexpensive front engine riders: There is the appearance of many choices at the big box stores in the $1000 - $2000 price range. The reason I say appearance is many of the brands are variants of the same machines painted different colors with other slight differences like logos and tire sizes. For example: Cub Cadet, Troy-Bilt, White, Yardman, Yard Machines, MTD, Bolens, Columbia and many store brands are made by MTD. Toro branded front engine riders from 2004 forward were the same MTD product as those named above. AYP (American Yard Products) Husqvarna makes most Sears Craftsman riders as well as Ariens, Poulan, Weedeater, Roper and some of the store brands. Most of the riders in this price range are mass produced and usually bring a decent value, hence the reason they sell so well at $1500 plus or minus.
So, what are the down sides? The quality of cut is not as good. They take twice as long to get the job done. That means they burn more fuel to get the same work done. They have a shorter life span both because of lower cost components and because they run more hours to get the same job done. That means they will probably have to be replaced sooner. Finally, is the value of the time of the operator. Every extra hour spent on the mower is an hour that could have been spent with the family or doing some recreation, or at work probably earning more than what was saved by buying a slow mower.
Summary: What happened to the front engine rider market: As discussed above the front engine rider market has become one where 98% of sales are now to the "What's the cheapest way to mow my yard that I don't have to walk" customer. There is still a small market that need and are willing to pay for a quality front engine tractor and they pay dearly for them because it is such a small market. Most of those who would have bought a medium quality riding tractor in the past are finding they can get more for their money, a better quality of cut and save a lot of time by going to a zero turn mower which are now mainstream and an excellent value.