I have both a 4 (with the original circuit board and no battery drain issues) and a 4ti. They're interchangeable as far as I am concerned - I seldom use flash and don't have an F280 anyway. The weight difference is negligible. I'd stick with your 4 and get it CLA'd.
2 black om4t's bodies went for $180 last night. :( I fell asleep and missed it.
I hope you got in on it!
I got the 2 champagne bodies a month ago and fixed them. :) same seller. But I've always wanted the black body version too.