i have an HV20, and have used a GL2 once skiing, but alot in video class. i do not have a lot of experiance with manual controlls (other than shutter speed, aperature, and focus)
heres what i think. I like the HV20, but really wish that the colors popped more. The 60i is nice, and you can get good slowmotion out of the cam (see here:
http://www.hv20.com/showthread.php?t=10718. that is at full framerate, and then you can go slower from there- i dont know how he did this but it explains somewhere on that forum). i wish it was a 3 chip cam though, because in crappy light, the colors kinda blow, but you can fix it in post. in good light, its find though.
one thing that i really like about the HD (ok, its not real HD, who cares, it looks great on my computer) is that it gives you the ability to zoom in on shots and pan across and stuff. if you export to a lower resolution than it shoots at, it still looks very clear (for example, you can zoom to 150% and export to 50% its original size, which is 960 x 540 or something like that, and it will still appear to be full resolution in the finished product).
when it comes down to it, if you know how to use cameras well, you can squeeze out great footage from both of the cameras. here is an example from an HV20, which i think probably sold more cameras than any canon add haha (look below)
i also wish the HV20 had a handle, but with the use of a tripod (use as steady cam if you dont wanna buy one) or a homeade handle, it is way more usable. also, a better focus wheel would be nice, but theres ways to get around that.
heres some footage of the HV20 used properly
-this one is mine:
http://www.vimeo.com/867915?  that is shot with a flourescent filter and a desklamp, no color correction. i was messing with DOF (this cam has a great DOF) and macros (great close ups as well). some of my other videos u can look atif you want, but they were shot on cloudy/grey days, so you can see how the camera lacks here
-thisis the rain shot i was talking about. its friggin amazing-
http://www.vimeo.com/431500