Hey there folks,
Just my personal experience here, maybe some of this will help.
I score to picture a lot. To lessen the lag issue I have found the following to help:
1. Convert mp4 movies to 422 ProRez
This will keep the processor from decoding the movie in realtime, and speed up performance overall.
2. Do not use the video track in global tracks
Disabling the video global track has increased the performance greatly, and lessened the GUI lag.
3. If possible, tweak plugins in a separate monitor
This only works in a multi-monitor setup. I find that if you open your plugin windows in another screen, the GUI lag lessens. It also helps to dediate that screen to plugin use. I have a screenset that I use just for intense tweaking that has an arrange window on the left and open desktop on the right
4. If on a single monitor, do not tweak plugins while the mixer is open
Don't ask why. This is bizzare.
I will log other things to help mitigate the problem. They aren't magic bullets, of course... but I've been able to produce 3 albums, score a film, and much, much more without feeling completely hamstrung.
This GUI....or whatever the **** it is.... problem is certainly a royal pain in the ***. if I can think of other solutions I've stumbled across, I will let you know.
Now, as for 32 vs. 64 bit...
In 64 bit mode some of the environment objects do not work correctly.
In 64 bit mode, many of the movie capabilities no longer work, (can't bounce audio to movie)
In 64 bit mode some global track functions do not work correctly
There are some other things I've found, but none of them kept me from still getting work done. For those working in film, this can be very important, though. i find it incredibly helpful to send sample movies to clients of my work so they don't have to line the music up manually....
I do find the cpu efficiancy and overall performance enhancement much better in 64bit mode, even though I find the occasional gremlin. For those who aren't using much RAM, I suppose 32 bit could still be cool if they are using mostly synths... but even Omnisphere, Reaktor, Kontakt, Play, etc, etc... they are sample based, so you need to be sure that whatever RAM allocation solution they use is compatible. (Such as Kontakt memory server for example)
I understand people wanting to jump to a platform that seems more stable. Believe me, i have thought about it many times... I know several composers who have already jumped ship... it's sad for me because i was the one who helped them switch to logic when logic made the jump to 8. :-(