sti black diamonds xtr tires on 850 xp

Ok bout to make up my mind I beleive ill go with the bd xtr tires but I can get the 27" cheaper than the 26" dnt make sense I trail ride hill climb rock crawl and play in creeks up an down water falls I dodge mud holes unless I have tu hit em tu get wer im going . So should I save 4$ and get the 27" or stick to stock 26" my 850 im sure will pull the 27"ers just fine rite without clucth kit im only be. 1/2" higher than stock . Do youns thank these tires will work good fer me