While I don't have a .25 springer, I too wonder at the usefulness of it. If anyone is going to build a springer with enough power for a .25, it's Hatsan...but even they use the same power plant for each model in different calibers. Comparing three "magnum" Nitro Piston rifles from the stats provided from Pyramyd Air: Benjamin Trail XL, Hatsan 95, and Hatsan 125 respectively. Benji claims "900FPS" in .25, but I think we all know you can usually subtract AT LEAST 200FPS from Crosman velocity claims, so let's say 700 (or less most likely). The 95 claims 650FPS, which in my (limited) Hatsan experience is probably pretty accurate, give or take 50FPS or so. Lastly, the huge-ish 125 claims 750FPS IN .25, which is also likely pretty accurate. If it HAS TO BE a .25 springer, I go with the 125 first (I prefer synthetic stocks though I fear the recoil mitigation system -SAS- more mechanical stuff to fail). Second, my nod goes to the Benjamin, but ONLY because I am confident in my ability to dramatically improve the trigger, and I can get parts for it very easily from Crosman (and potentially convert it to a .22 cheaply and easily if I'm not satisfied with it's .25 performance). With that rifle, I would likely search for lighter weight .25 pellets to shoot (as it will likely have the lowest velocity of the three). Getting parts from Hatsan can be a hassle.
So it all boils down to how you're going to use it? I'm going to assume you're looking at a .25 to hunt, not plink? As mentioned above, depending on what you hunt, you may be better served by a .22 from any of the three. Flatter trajectory at longer range, and likely similar energy from a heavier .22 pellet. Something else to note: these are all "long stroke" springers, meaning more power AND more recoil.