Let me ask you - when you buy a car, do you choose a manual widow opener or do you skip on the navigation system just because it is one of the electronic parts that can potentially break?
My point is that while everything can break (nothing is forever), certain things we get used to and do not want to be without.
To answer your question - while the power recline does break once in a while, the rate is very low - about 2% (statistics from Berkline). Most of the time when something breaks, it happens during the warranty period, and should you have a problem you would get a replacement component within reasonable time frame. If you are so unlucky, and a problem happens outside of warranty period you will be able to purchase a replacement part, and it will not be that expensive...
Regarding the comfort of the 13174s and 13175s:
Both are very comfortable recliners, but comfort is such a personal and subjective factor... The 13175 is very popular among those who wish to fit more chairs in the smaller rooms, and the narrow footprint of the 13175s allows for that. The 13174s will take more space, but they also have wider armrest that allows for larger elbow space. One more thing - the 13174s are chaise design recliners, and the 13175s are not. Functionally they both will provide a nice leg support, though.