Yes, if you're in tons of channels, treebar makes more sense. Personally, I just stay in channels where I either offer help/support or chat with friends, so the number of channels I am in is far less than some others.
I *might* consider using the treebar if it offered background support the way that the switchbar does. Since I can't really theme it to match the rest of my mIRC, I don't really care to use it. I'm sure there's a DLL somewhere that can do that, but I don't want more DLLs than I already have. Anyhow, just personal preference.