I ride both 26" & 650B , 26" won more world cups any any other wheel set! Steve Smith switched from 650B back to 26" and won DH championship (I put the vid on here) If you talk to any old skool MTBer most will say it's all rubbish! 1 example my old man has ridden all his life from road racing to XC MTBing, my brother has recently brought a entry level 29"er,he showed it to my dad and he just cracked up saying it looks "stupid", Some people just don't like "change".
So what do I think, well you pop down your local bike shop and try to find a 26" wheel base MTB ! 650B is the new 26" Is it good for us I think so, there's more choice than ever before, to much in fact (XC,TRAIL,ENDURO,ALL MOUNTAIN,FREERIDE,DH,29er,650B) The bike industry has grown,which can't be a bad thing seeing as we all enjoy riding!
Ultimately it all boil's down to personal choice ! I went for a 650B, I noticed the tweak's in the frame's geometry (lower center of gravity) more than the larger wheel set! They did help with climbing tho!
Would I buy a 26" bike again ,hell yeah if I liked it! resale value doesn't bother me, bike are worth F**k all second hand now day's anyway!, This question is a true head F**k as there's no true answer for you mate! Have fun choosing MATT