This may not be quite the right forum, but I know the site demi-gods will move this thread if needed. Basically, I'm curious why you would use a buff frame addon if your unit frames can display them. Personal taste? Performance, easier to config etc... The one thing that comes to mind is the unit frames could get crowded if you have a lot of buffs/debuffs.
I'm not trying to start a flame war or promote one addon over another. This is just something I've been curious about for a while.