FWIW:

I have had the Imate, treo, and a Nokia 6620. My son has the Razr and
can make calls in fringe areas more often than me. BUT in the fringe
afreas, he drops more calls once the call is established. Not many,
but still more than me. I have not dropped a single call ONCE I get
through with my Imate (sx66). Another thing we have noticed is that
he does not drop the calls IF he does not use his BT headset in the
fringe areas.

That sounds normal.  My RAZR and Nokia 6620 and 6230 have far
better RF than my Treo 650 on Cingular.  I live in a fringe area on an
island so I tried out a ton of different phones to see what would work
here.  The Treo was useless unless I went outside.  My wife settled
on the RAZR and I on the Nokias.

The difference may be due to SIM programming -- you can only meaningfully
compare two phones by using the *same* SIM in both phones.

For example, if one SIM is programmed to "home" on "blue" (old ATTWS network),
and another SIM is programmed to home on "orange" (old Cingular network), then
one may work better than the other in a given location depending on which
network has the better signal in that location.

When Cingular completes network integration (expected in mid-to-late 2006),
there won't be any such distinction.  In the meantime, ENS (64K) SIMs and
ENS-capable handsets make it possible for Cingular to change the home network
OTA (over the air) between blue and orange, which might result in better (or
worse) performance in a given location.