You seem to have overlooked the quality of lens available between the HVX and the Varicam, this will make a big difference to image quality even when viewed on a large screen.
I’ve shot side by side tests with the Sony F900 version 3 (1080 25P) and the Varicam at 720P using Canon and the results compare favourably, the HVX with its cheap lens won’t come close to either of these.
You need to consider the marketing strategy for the HVX camcorder, Panasonic or Sony could get together with a major lens manufacturer and make a smaller camera with interchangeable lenses, furnished with all of the functions of their larger counterparts but where would that leave the sales of the F900’s and Varicams?
I like working with my Sony HDV, it’s small light and cheap, but I’d never consider it as a replacement to a larger camera with real lenses, I just don’t think the HVX will be as good as everyone is anticipating.