After seeing Brazilian Oregon chain hitting the market I'm a bit wary of buying individual loops of Oregon without seeing the original 100' packaging. Who knows what the hell you are getting. The Brazilian made Oregon semi I've run (still have about 80' in the shed) is absolute crap.
Personally I really like the LGX I've used and rate it as the best out of the box full chisel chain I've run, closely followed by RSC. The fastest full chisel chain I've ever run outside of square though is actually Carlton A1LM that I hand filed. Funnily enough I don't actually rate Oregon Semi Chisel compared to Stihl or Carlton (or the older Windsor).
I use 7/32" files on all 3/8" chain regardless of brand and interestingly a few softwood fallers I spoke to in S/E South Australia were also running 7/32" files on Stihl chain. I've tried 13/64" and never found it really made any difference but personally I do like the larger gullet with a 7/32" file. On new Stihl chain though a 7/32" is a tight fit between the back of the depth gauge and the leading edge of the cutter