My input devices on my iMac 27":
Apple wireless keyboard
Apple wired keyboard
Magic Mouse
Magic Trackpad
Razer Orochi
Logitech Performance MX
Logitech G13
Yes I know, kinda ridiculous. Helps vs. carpel tunnel though!
I predominantly use the Razer, since it's small, light and really precise. I use the trackpad mainly for gestures or leaning back and browsing (I LOVE the two-finger double-tap to get a nice zoom going in Safari) since I got the Twelve South Magic Wand.
I use the Magic Mouse mainly for my MBA since I feel it's not fast enough or precise enough for my iMac. I also dislike the ergonomics, it has great features but it just isn't comfortable. My hand isn't flat like it is.
The Logitechs I use very uncommonly. The Performance was my main mouse until the Orochi arrived, and the G13 is for games, but I have trouble with playing them well with it.
Anyway, Trackpad over Mouse.