Quake Live: I heard there was quite a discussion on that when it was first released. Something about the game having minor changes that do effect the overall feel which separates it from the original quake? I personally never was a quake fan. Haven't tried the new title. :/
I think it's pretty much the same, ~old skool.
Now, the big difference you will re-spawn with 2 weapons (with limited ammo) of your choice. I like it more.
And they changed the voice which is very bad imo unless you like rainbow.
Overall, one of the best game when you want to kill time : fast and furious.
(I play FFA Chicago or TX server.)