Here is my experience with 29'er - just one persons view point in an evangelical war....
I am around 5'9", moved from multiple 26" 's (soft and hard tails) to 29er (hard tail) and ride XC. Recently we got my wife a 650B Merida. The 650 is slightly lower price than the 29er - and my favourite 26er I was riding most is an old/classic from Mid 1990's weighing under 10kg
On non-technical ground and fast flowing single track, the 29er is not a bad bike. Once the corners get tight the 29er is, "a difficult child". It takes effort to initiate turns and get it do what it should do. Maintaining precise lines though corners next to impossible and even on straights I have to concentrate on holding the line. I initially put it down to geometry differences rather than wheel size (but I have ridden many 26" and never had this problem) as everyone was telling me how great 29er's were, how could it be the wheels. Then I rode my wifes 650B on those tighter technical trails. I will never again buy another 29'er. I now ride my wifes 650B when I head out on technical stuff if she not coming with me.
So is the difference wheel size, or geometry - my guess, 50/50. The way I see it the 29er was a failed experiment in bigger MTB wheels that made the industry a fortune with people doing upgrades. The 650B is a much better wheel size of a majority of riders, hence the move by the industry towards it. In a few years 650B will be nearly as ubiquitous as 26" was - for good reason - and only very specialised and custom builds will have 29er. Smaller frames may come with 26" just like youth bikes have 24".
I will keep my 29'er for non technical XC and unpaved road riding, but will not take it out for serious XC.
As @Batman suggested - rent a 29er and see if you like it. My guess is its a love it or hate it kind of thing, not something you sit on the fence on.