If you are to compare it to Rodinal, then yes, you will indeed get better shadow detail. Simply put, Rodinal is not exactly known for delivering full emulsion speed from any film, at least not without driving the contrast up higher than most people prefer. When I want to use Rodinal for a specific purpose, I will always give a more generous exposure than I would if I plan to use XTOL. But will XTOL deliver up to 2/3 stop more speed than say D-76 or something similar? No, I haven't seen that. The best I've seen is about 1/3 stop, and that can be pretty hard to see in a lot of cases.
