Premiere/FCP user here, and I was thinking about finally giving AVID a try on a new project.

Working with 5K RED footage, how is the AMA? If I transcode to Pro Res instead of
DNxHD, will I be okay? Am I taking a performance hit?

Media Composer supports Pro Res or DNxHD. Both work great.

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Gary

Dnxhd is a great codec and I use this for almost most of my Avid edits, I'm on Mac. You could also transcode to ProRes and then AMA, then consolidate. I do this a lot now as I'm receiving a far amount of ProRes files from clients and this is very fast. Avid handles ProRes natively.