There's no question the wedge on the beam is better, and even better is a hydraulically adjustable wedge on beam with side wings for a 4 way split.
But unless you have a log lift, you aren't going to split big stuff that way, and a lot of what I get is 30-40" oak. That's not getting lifted onto the splitter! I can wrestle that onto the splitting foot and get it done. Otherwise, I'd have to forego a lot of free wood. It's all about what your needs are, which includes what you are going to be splitting.
On that note, this cracks me up:
Compare that to a 40" oak crotch!
But on a serious note, again, it's all about what you are going to be splitting. If 24" fir is big to you, then a 22 is probably good and a 27 will do just fine. I'd be
crying with one of those smaller ones.
Know your wood and buy accordingly.