When I bought my 38 acres a little over a year ago I had to start shopping for a tractor. I got some advice from trusted people that 2wd was all I'd ever need. However my gut told me that 4wd was a good thing to have.
When I bought my tractor I made sure it had the 4wd and have found it to be in my opinion, essential. I have some good hills on my property, some mild drainage ditch's and one area that stays a little wetter than the others. All combined there have been a 'few' times when going over the property hogging that I've had one front wheel in the air and one back wheel slipping. Hit the diff lock and dropped it into 4wd and slowly eased my way out.
Other times I've gone into a little ditch that was probably 15" deep with fairly sharp sides, something that a 2wd might've had an issue with I suspect, and it just pulled right on through it.
Could I get by with 2wd? Yep, I'd just have to be a little more careful and cautious than I already am. I need all the help I can get as a newbie tractor owner and the 4wd just gives me a little more margin.