You would actually- if the hills were too steep for 150’s 
/seconded!
I live on the Pennines - there are hills here I can’t get up with the 150s on my 29er. I am glad every day I ride that I didn’t go for the 125s on it. 
Some of the hills are so steep that I’ve wondered several times if I’d be better with a 26er 
It’s become clear to me that some people on this board have no experience of steep hills
(see this thread for recent examples- I finally rode a mile
I really don’t understand why some people insist that the kind of steep hills we’re talking about that require 150mm cranks on a 29er, can be climbed on a coker with 110mm 