That is a very big difference. Surprising, as I would have expected the difference in dBm to be pretty much the same regardless of absolute signal level. But perhaps that isn't the case in an area where signal level is very low. Or perhaps it is/was a bad handset.
I actually considered all three of those phones. The Mot phone just seemed clunkier, and I really didn't care for, or want, the slide out key pad. Although the Mot Droid is a noticeably better performing phone, I chose the Eris for its sleeker design, slightly lower weight, and the touch-screen. The difference in performance didn't seem that huge, to me. But if I start having signal problems, I will probably change my mind!
The Storm II was the bigger contender. I debated between the two for quite some time. I didn't care for its touch screen, and it was also bulkier. The global capabilities were a plus, but I wouldn't use that enough to make a difference to me.