stella--yeah? I kind of like that the tektro hangar locks into place. It kind of makes the adjustment screws redundant.
knucks--34.7% less powerful. No, I don't know. With this style of cantis, there are a lot of variables that affect the braking power--how close the pads are to the rim, how high or low you put the straddle, how wide the straddle is, etc. But I do think, on the whole, that the avids are stronger, if a more on/off type of brake. The 720s really give you quite a bit of modulation. Which means you don't lock up the wheel, but you don't need to lock up the wheel.
I actually think the "strength" of the avids might contribute to fork chatter and squeal. I was running the stock avid 4s with dual compound black/salmon mtb pads, and they were super grabby. Since chatter and squeal are just oscillations of pad grab and release, that would make sense. Like I said, no such problems with the 720s.
Plus, they are fairly inexpensive, and by my lights quite well-made, so what do you have to lose? However, if you are loath to spend the ducats, you may not appreciate the extra mud clearance the 720s afford, and might be just as happy with the Avids or even mini-Vs
You may also want to try the Kore brakes shipping with Jamis Supernovas and a couple other bikes (maybe the high-end Kona Jakes)