How big are you?
The reason I ask is that in my experience, one of the ways you can size the uni to the person is by size.
If you were to make a muni decision matrix, include the following based on your current riding:
Size: Small, medium, large
Strength: weak, average, superman 
Riding preference: stamina, power, grace
Riding style: roller, hopper, combo
Age: younger, older, really friggin old
Experience: new, novice, intrermediate, advanced, da’ bomb!
Spin (crank) preference: short cranks, medium cranks, long cranks
Tires/Inflation: narrow/high pressure, fat/low pressure
Riding speed: Slow and careful, fat and furious
Use: XC, single track, downhill
I’m sure there are other things you can throw in the mix.
For example, me:
Large, superman 
, power/stamina, roller, older, intermediate, long cranks, fat/low pressure, slow and careful, single track/downhill
My muni is a 26" Surly Conundrum, Large Marge Rim, Surly Larry 3.8" running 10psi, 170mm cranks. This uni is heavy, very stable, big soft tire for rolling over obstacles, fairly tall (nearly as tall as my 29er), so it’s a lot of uni to handle, so I run long cranks. But I’m 6’, 200#, sz 13’s, and I have the power to throw the uni around.
In contrast, my son is 6’ 3", 145#, sz 13’s, and thoug he’s not a wimp, he finds my Surly to be a bear of a uni. He rides a KH 24 x 3 with 160 cranks, however, hewill probably upgrade to a 26 x 3 this summer cuz the 24 is just too small for his height; he complains of spinning out on the 24 and not being able to go fast enough.
My XC is a KH 29, KH Freeride Rim, Racing Ralph 2.4 running 18-20psi, 165mm cranks. I can really whip this uni around, but due to the narrower tire, it’s really not great for rolling big obstacles, so I use it for smoother single track.
The Surly is my go to uni when the trails are nasty, though I find that I like it for most anything, though admittedly I get tired faster on the Surly than on the KH 29. So the 29 is really my XC ride.
I used to ride a 26 x 3 for everything, only added the 29 for XC this past year. If the Surly was too much for me, but I still wanted a true muni I’d be back on the 26 x 3. Though I like my 29er, I find that it is a little too tall and slow for technical muni. I never realy liked the 24, find it to be more like a trials uni than a muni, it’s just too slow, pedal strike is an issue, and I find them twitchy at speed. Granted, they work great for hopping and they are easier to throw around, but consider how you will ride the uni, ie getting to and from the tech parts of a trail, a smaller uni sucks for riding miles on jeep roads but is fine if you hike up a ridge to get a technical downhill.
In terms of potential performace and materials strength, a 26 and 24 are no different, they can both hande big drops, hard knocks, etc… and the weight difference is minmal when set up the same.
Long post, sorry about that