Do you have the Hydraulic Taps?
If you have the hydraulic taps and plan on using those you are limited to about 8 gpm and your splitter will be slow. You can mount a Prince PTO pump and get the speed up. Having worked with 3 pt hitch splitters there are a few things I can warn you about.
First, they are low, so you're stooped over all the time, but the good side is you can get a big round on the beam without lifting it 2 feet.
Second, they weigh a lot and you may need to add ballast to the bucket in order to safely drive around with the splitter mounted.
Third, forget about maneuvering in the woods. Between the bucket in the front and the splitter hanging off the back I found I had to be very careful about getting hung up and how I approached turns.
Fourth, if the splitter is mounted on the tractor, you can't use it to bring wood to the splitter. I use my bucket almost like a log lift and feed table. Load it with wood to be split drive up to the splitter on the side opposite where I'm working, get the bucket even with the I-Beam and just pull the rounds on with a pulp hook or pickeroon. Makes for a slick system.
Anyway I find it much faster to use a separate powered splitter but there are the added maintenance costs and higher up front cost when purchasing.
It all depends I guess like everything else associated with wood, how much do you want to spend, how much will you use it, and will you regret what you bought and spend more money buying what you really need / want. Can't help you with that one.
Are there any particular models you're looking at? Several members here do use PTO splitters and may be able to give you first hand feedback on the particular unit you're thinking about.
Take Care