I did some comparisons a while back between 6 an 8. I did only single files though and not whole shows but the difference was not that big. I used to always use 8 but it takes fucking forever.
yep, i just tested and had a nice post for ts.com on comps, and it got erased before i could post it somehow
\but anyway, the biggest difference was between 1 and 3, l;ets say the original wav was 707 MB, the flac-6 was 458 MB and the flac-3 was 458 MB(same damn compression) but the flac-1 was like 470 MB(12 MB diff from 3/6), and then the flac-8 was only 1 MB higher than the flac-6, at 459 MB
so no huge differences unless youre running flac level 1
personally, IMO, i think your best bet is flac 6 because of encoding speed and decoding speed, flac-8 takes my comp too long to encode on, but I dont know about yours!