I gave it a lot of thought when I was considering buying a splitter. I settled on a Ariens 45 T with a suburu gas engine, from Home Depot at $2000, then used one of their 10% off coupons.
As the earlier post stated, it frees up a tractor to load logs, or do other things, I move my splitter around with my UTV, and its easy to manuever around and can get into tight spots where a tractor cannot. It is also easier to move the wheeled splitter around a shed or barn when storing, whereas a 3pth you have to hook it up again.
These were my advatanges for a pull-type, but others may have different situations