How much wood do you need to split, do you know the gpm required to operate the splitter you are looking at. If it's a cat 1 splitter from a s/cut it probably needs 10 or more gpm. I think the Case is the only gt you mention that flows around that rate. Still a 1-way splitter can be slow, increasing the hours on your tractor engine, hydraulic system, etc.
The Case 2-way splitter is faster, reducing run time, these tractors aren't getting younger. Case splitters are rare and expensive. Add in a couple hundred for a rear pto, plumb in a case drain, etc, and you could get probably get a new tow-behind splitter for the same price, save a lot of run time on your tractor. Or get a used one off craigslist for less. Some of them stand up in the corner out of the way when not in use
Only extra maintenance on a tow-behind would be an extra engine oil change. You'd still be changing the tractor engine oil more if you were adding run hours by powering a rear splitter.
If the engine on a tow-behind ever craps out you can just get a generic 5 horse motor off craigslist for cheap, or a couple hundred new from an online supplier. Otoh if you wear the engine out on a tractor with extra hours running a pto splitter you have to find a 14-hp Kohler or whatever that will fit your tractor's frame, pump, pto, etc. Or rebuild your engine, hydraulics, etc. Or spend 2k for a repower kit. To me it seems cheaper and easier to pick up a used tow-behind for 500 bucks.
Of course if you're splitting under a cord a year GT splitter might be fine, just my .02 good luck