In your case, I'd go for 27.5. You have better parts options once you upgrade. I believe 26ers forks & wheelsets are starting to get scarce, they probably stop coming up with newer and improved versions. And when the time comes for you to consider a 29er, it is easier to sell a 27.5 than a 26er. Besides, you get to experience the new wheelset, which, imho, is a better ride than 26er.
Personally, I jump right into 29er from 26er and didn't look back since... ah well, granted that l didn't have the 27.5 option when l made the switch. I did looked ahead though, currently on 29+ & loving it.
Btw, I'm bias toward Carbon Speed, more on customer service... both pre and after sales service. Frames are good quality too. Have 4 of 'em, including a custom Ti they facilitated. Like you, I'm not much of a geometry guy either.
