Dunno how tall u are but the X27 is a longer shaft than the x25, so more leverage/speed and be more suited if ur taller.
I'm only 5 10 and the 27 is fine for me, but I do have a good swing, far too many years hand balling fences swinging Mel's.
The shorter shaft might be nicer to swing if ur not used to swinging stuff.
As for mechanical splitters, id say it depends on the splitter and yr timber.
Many of the cheaper 1s are about as quick as a week in jail.
I have just modified/improved my spkitting bench, build a sleeper into a banking with breeze blocks so spkitting at waist height and all logs at that height no bending down.
I dump the cord wood/rings at top off bankng log it and they almost roll down to splitting area themselves.
Let gravity do the hard lifting.
Makes the splitting effortless, not many log splitters would keep up.
I'd be cautious of watching too many internet bids wether axes or splitters, they always look great,.
But look at the wood their splitting usually beautiful straight grained small logs, most grannies could look good splitting them