I'd rather see "Genesis of the Daleks." That's a really pivotal one where the Baker era is concerned, and it arguably sets up the Time War arc from the new series.
GotD was probably my favorite of the Baker era, but because of the length, I didn't think it would be a likely candidate. But I agree totally with you that it was the pivotal story, to be sure.
Oh, and this is off-topic but I finished reading 'Watching the Clock' this afternoon and thought it was great.