As for particular songs, i will generally first give a listen to a studio version, and then, after a number of listens move on to some bootleg. Interestingly, even the poorest sounding bootlegs give me something "new", in terms of dynamics, emotions, energy... Once i get familiar with the live version of a particular song, i may switch back to studio version every once in a while, but live performance remains my preferred version.
However, as with any other band, there's a number of "mannerisms" that can sometimes irk me, or at least make me feel sorry i cant have some details my way. For instance, i never found live version of
When which accentuates the words "grin" and "aware" (in "the gilded faces grin, aware of my final demise...") the "right" way, and Mike seems to sing this part each time in the same way and that's when i just wish he would make a change in vocal phrasing at least once. I know its picky, but it would mean to me a lot. I especially crave for a live version of
Master's apprentices and
April ethereal which will have the extended outro, with those ecstatic repetitive chords... I understand its clever to shorten these songs in numerous live performances (especially since its impossible to do the gradual fade out), but i feel that in some official live version (as on
Lamentations) there could be one extended coda for the full impact. This way it can feel like a too short orgasm
But, these are minor quibbles, of course.
Overall, i think Opeth is the greatest of live bands, and i pay just as much attention to their bootlegs as to their studio work. I think studio versions are sort of "ideal" versions, like perfect thoughts, but i usually find real and "flawed" charms of live versions all too appealing.