It would take pages to detail all the situations where 4WD makes a huge difference.
I would NEVER purchase a CUT without 4WD
The only time I do not use 4WD is for road travel. On occasion after getting off the road I forget to go back into 4WD...when that happens it's not long before the tractor starts slipping
I agree with about everyone here. the only time I am in 2wd is mowing (with the loader detached), and roading.
My father has a JD 2040 2wd. It is a larger tractor than my l3400. His has a 6ft bucket, 14.9 x 28 tires filled (about 1000lbs total) and he can even have an implement on. I can work circles around him unless it is very dry and very hard. A load in the FEL of the 2040 makes it a very difficult task to back up.
And forget about moving much snow with it in the winter.
I wont say 4wd is a MUST because they got by fine without it for many years, but for those of us that have used a 4wd tractor, woner how anyone cound get by with 2wd.
I don't think it has been mentioned yet, but I will add that 4wd also guves you 4 wheed breaking to. Which van be nice going down a hill in the winter with a trailer load of wood behind.
So you don't hate your tractor (and yourself for buying 2wd) for being incapable of working in crappy situations with lots of mud, manure, snow, or all three mixed together.
Traction: Was digging a small bank out, and even in 4wd, the rear wheels would start to slip, so lock up the rear axle. My FIL before he passed told me "Don't you get a 2wd tractor, you will regret it." I didn't, and I am thankful.
Braking: Shifted it out of 4wd to drive it home, and on the way down the hill (asphalt driveway) braking for the end locked up the rt rear wheel. The braking is much better in 4wd!
smaller tractors don't have individual rear brakes. having the front wheels pulling gives you a lot more steering in difficult situations similar to what you can get by riding the left or right brakes on a rwd larger tractor.
also helps with steering when diff is locked and tractor tends to plow forward in a straight line.
totally true about braking going down hill. when the ***** end is light like with a heavy loader load, the only way to slow down or stop is if you have 4x4 engaged or you drop the FEL.