Roadie looking for a trail bike

Hey guys. Basic old question, looking at a first serious MTB coming from a road/track and a little bit of cx background. Looking at trail bikes, I want something versatile that I can develop some skills on and passably do a few XC races, maybe a bit of bikepacking. No FS.

Tried out some bikes and was surprised to find I liked the [Diamondback Sync'r Pro](https://www.diamondback.com/sync-r-pro-4021) in spite of its smaller wheel size and aggressive angles, given I'm a tall dude coming from a road background. But I am guessing the advantages of a 29 or 27+ will become more obvious out on rough stuff? My other main consideration is the [Fuji Bighorn 1.1](http://www.fujibikes.com/usa/bikes/mountain/trail/bighorn/bighorn-27-5-1-1), near identical spec but steeper HT, lighter, and with a 27.5+ I'm sure I could swap for 29 if I wanted. Industry discounts limit my realistic options to a few brands.

So do you guys have any input on what these will be like out on the trail? Any red flags about either of these? I like the versatility of the Fuji; it's lighter, more versatile, more appropriate in theory for my use case, has better brakes, and is a bit cheaper. But at least based on my little parking lot test against a (different) plus bike the Sync'r just seems like it might be more fun. Perhaps this is just the wide bars/short stem?

**TL;DR:** am I just having analysis paralysis over a wheel size thing that doesn't matter, or is one of these legitimately going to be better for my general purpose needs? Also do all 27.5+ bikes fit 29" tires?