I had a TRc with 26" wheels for awhile, then put 650b wheels on it, then I bought a SOLOc, so I can provide my personal comparison.
First of all there were some setup differences between the bikes. The TRc had Easton EC70 bars, 685mm wide. I originally used an 80mm stem, but had trouble keeping the front end from wandering and lifting on climbs, so I switched to a 100mm stem, which worked well for me. The Solo has Easton Haven bars, 711mm wide. It originally had a 70mm stem, but I swapped to an 80mm stem. So bottom line, the Solo has wider bars and a shorter stem than the TRc did. The Solo also has the new Fox CTD fork and shock, compared to the TR's RLC fork and RP23 shock.
Climbing: The Solo climbs better -- less bobbing and the front end stays planted better.
Pedaling efficiency: The Solo pedals more efficiently with less bobbing. This could be due to the new VPP pivot points or the Fox CTD shock. I suspect mostly the latter, since the bike also lost some plushness compared to the TRc. On the TRc I had to add air to the rear shock (reducing sag and not getting full travel) to keep it from feeling wallowy in the mid-stroke.
Playfulness: The TRc felt more playful and more agile -- easier to lift the front end, easier to manual.
Descending: The TRc felt a little better on rough descents. I think this is mainly because the fork and shock were plusher.
Cornering: For some reason I felt more confident pushing the TRc harder in corners. Since the geometries are pretty much the same, I'm guessing this is due to the different cockpit setup. The TRc absolutely railed the turns, both with 26" and 27.5" wheels. The Solo corners great too, but I just don't have the confidence to really push it like I did the TRc. However, my local trails have been pretty dry and dusty since I got the Solo, so this could have something to do with it.