I just went from the 10HT to the HD20/PLV-70. My 10HT was destroyed by some water leakage, so I really didn't have a choice.
I boil the whole thing down to this. Sanyo is a technical powerhouse. The brightness, contrast, screen door are all impressive. What Sony lacks in sheer power they make up with in elegance. The GUI for controlling the projector is just top notch. You will feel like you're taking a step backwards when you leave Sony. Functionally I think Sanyo actually does more, it just seems clunky to navigate.
I can also say Sony always seemed to have top notch scalers. When I had the 10HT I never felt compelled to get a seperate scaler. On the other hand I know many PLV-60 owners did. Of course the scaler in the PLV-70 is actually pretty good. I'm happy with it, most of the reviews I've seen have been pretty positive. But don't expect a huge jump in quality with you're SD content, other than brigtness and contrast if you make the switch.
(On a side note, I've often wondered if Sony was tweaking the focus a little when it switched between SD and HD, because that's what I do on the Sanyo and it looks a lot like the results I had with the 10HT. Sony LCDs auto focus)
Sony has better manuals, an actual program that shows you how to construct control commands for the serial port, auto focus, a CD-ROM with PDF manuals, and a great screen/PJ setup program that creates CAD quality drawings of screen and PJ placement.
But when it's all said and done you have to decide between pure power, and all the little details. Most of the time you aren't in the GUI. You're watching movies. It was an easy choice for me as I had a fat insurence check to spend, but honestly, unless you had ambient light issues you needed to contend with, I'd stick with what you have until LCDs that can render a 1920x1080 come to the market.