It really depends. If a group literally takes pictures of pages and edits them on paint, I'd go for the better quality group. But if the better quality group releases once every 10 years I think I'd just work with shit quality scans.

Favorite Art:
Oboreru Knife
19 Days
Gangsta

Lol that's an amusing thought. "10 years" The internet has only exited widely for over two decades

The first ARPANET link was established between the University of California, Los Angeles (UCLA) and the Stanford Research Institute at 22:30 hours on October 29, 1969 but that is hardly mainstream and 1989-ish would be the time when the internet started to become recognizable. Here is an interesting infographic on the topic [url]http://wikipedia.org/wiki/File:Internet_host_count_1988-2012_log_scale.png[/url]
(the ever popular Doom came out in 1993) and i first connected in 97.

Project Gen form 1976 could be the father on modern scanlations i guess and there were (horrible) fan subbing groups in the 80s for anime too. The garbage i got to watch on VHS...

Edit: The world's oldest analog Computer dated between 150 to 100 BC

Kibyōshi- the first purely adult comicbook in Japanese literature from the Edo period
Scanlation when?

I also read EU/US comics and am a librarian.
Manga-Masters, My ANN-Lists + Imdb

When hyperbole goes rael.

Favorite Art:
Oboreru Knife
19 Days
Gangsta

The current question is kinda unanswerable. Partly because it is not specified how much slower the old group is, partly because it is not specified how big the difference in quality is (or simply how bad the quality of the new group is).
If the quality of the new group is abysmal, I'd definitely wait for the old group's releases. Unless the old group is so slow that one has to fear they discontinued the series each time, while the new group basically already finished, in which case I'd probably read both. If the quality of the new group is actually quite similar: sorry slow group. Same if the quality of the new group is quite decent and the release speeds are miles apart (as in, once a week vs. once every 2-3 months). In that last case I might read the slow group's releases once they're finished if I enjoyed the manga so much I want to read it again.
All this provided I know about both groups, their speeds and their qualities.

Last but not least, I try to avoid manga that haven't been completely scanlated/translated or that are otherwise incomplete, because I hate being left hanging (especially if there's no or little chance of time fixing that, like if the mangaka discontinued the story or even died).

As for the previous question. I'd go with the majority. Except or Rahxephon. I downloaded the opening of that anime onto my harddrive because I like it so much.

"The problem with defending the purity of the English language is that English is about as pure as a cribhouse whore. We don’t just borrow words; on occasion, English has pursued other languages down alleyways to beat them unconscious and rifle their pockets for new vocabulary." --James D. Nicoll