The question is, will the 25HP tractor be able to maintain 540 RPM at the PTO at a reasonable speed (intake of snow). With fresh light snow on a crisp morning, likely yes; with the heavy wet mess we can get and with what the plow pushes in at the end of your driveway, maybe not. I cannot say for sure because I have only had one tractor and can apply up to 45HP to the PTO to a blower rated for 35HP. I typically run 2000 to 2200 rpm when blowing.
If you are like me and only plan to buy one tractor in your life, get more HP and be more confident in your ability to do all the jobs you want to throw at it. That said, at least you are looking at a good frame size in the CK2610 and CK3510 with equal hydraulic lift capacity.