Depends what type of riding and what terrain you ride on.
I don't think the stock 25" even run true to size do they? (as in they run small)
If it was me I would go with 26" and keep stock clutching and call it a day. but again, it completely depends terrain and type of riding. I have an Outlander that came stock with 26" that run small, when I replaced them I went with 26" that run true to size (hard pack trail tire, nothing extreme) and I feel these are much closer to a perfect sized tire for the machine....maybe even 27's. I just see it as very common for people to go 1 size up from stock all the time when they replace and be very happy with that. If you do fast paced trails then maybe just the stock size, but since you do snow and mud I would look at 26's....something better than holeshot's also.....