Having to size new brass and fire form every case is the reason I would not choose 6/6.5 SLR. I do like the 30 deg. shoulder and long neck but don't feel the added benefit of these features is worth the time and effort givin the fact that there are plenty of other options that have comparable performance, don't require as much case prep, and thousands of people are not bitching about them.
You don't have to fireform at all. The case prep is no different than any other regular cartridge - you can sort, turn, cull, anneal, uniform and otherwise prepare your brass to the extent that your accuracy needs require. You have to do this with any cartridge.
The ease of finding an accurate load with the 6SLR is notable. It is NOT a velocity winner, it is not designed to go faster than a .243. It does shoot the 115's faster than the XC at more reasonable pressure levels. Like anything else, it should have decent barrel life if you load it accordingly.
If you are shooting 105-class bullets, just stick with the XC. If you are shooting the 115's, it's worth consideration to use the SLR. It's what the .243 should have been but wasn't.
Arguing about which is "better" in a practical precision rifle scenario i.e. the .260, 6.5 Creedmoor, .243, 6SLR, 6XC, etc is wasting breath. It's like arguing about which is the better deer cartridge out of the 30-06, 270 Win, 25-06, 7mm Rem Mag, etc. The differences in performance are marginal compared with the variation in shooter ability, ammunition quality, and shooting system design. If you think otherwise you need to put down the supermarket gun rags and start shooting some place besides the 100yd table.
And.....yes, I won a match last weekend with the SLR using 0x fired Winchester brass and my standard load with 115's.