I like the 100, not for volume but for the girth and punch. The gain is derived from the preamp so the 50 is no slouch and will have plenty of volume, but to me the 100 sounds bigger. Both are killer though and neither is night/day different.
I’ve never played the 50, but when I had my 100 I preferred the 100w mode compared to running at 50w. As mentioned above I found the 100w mode had more girth and punch. Could be different in an amp that was designed to be 50w rather than the half power option on a 100w.