I am just getting started mountain biking and I have a few questions on my first real bike. I am primarily looking at hardtails as my budget is around $1500. I have been looking at a few different bikes but I do not know if I should be looking at a 27.5 or a 29er. I am 5'9'' and 115lbs and i'm not sure if the 29 will be too big for me. I am planning to buy a bike either used or at the end of the season so that my budget can stretch a little. I would also prefer to get a bike that will last me a while or a bike that is worth upgrading parts on. Any advice on wheel size or which bikes I should be looking at would be greatly appreciated.
Wheel size is largely a preference based on riding style. Where 27.5 works well on all adult size frames, 29 may not work as well on some XS/S frames so some models may have wheel size based on frame size like 27.5 on XS-M and 29 on M-XL. Generally people will say 27.5 is agile and playful while 29 roll over terrain easier and inspire confidence. Here is a great article on the topic...
I'll be the outcast, and say that if you're 115 pounds, you probably aren't built like a brick shithouse - so the LESS wheel you have to turn, the better off ya are.
Nothing wrong with 26's. Been on them for 25+ years - and some - that I rode as a young buck at probably 150-ish lbs....had 24" drive wheels.
I'll even check my bias on this one - I really don't like the bigger wheels. Period.
Frankly, I like the ratio of cadence to wheel movement of a 26. anything bigger seems lazy and un-energetic to me; and even at 180lbs, I simply don't have the leg power to make the big wheels feel as exciting. Yeah, a lot of it runs on final drive ratio, but I'm also not a big fan of the stupid new million-gear drivetrains either. Up to you. Anything is possible!
Don't worry about it... if you have a few bikes in mind and some are 27.5 and some are 29 (or some come either, ie: Norco Fluid HT) then get out and test ride them and pick what you like.