Need Advice Selecting Cellular Service

I live in the Wash DC area and travel to the Boston area alot (Cape Cod). I get alot of dropped calls or alot of blind spots with AT&T. Which provider has the best coverage between DC and Boston? Also problems with echo and problems with my callers being able to hear me but I can't hear them. I'm using the AT&T Ericsson Pocket net phone model #R280LX which I think is terrible. I like being able to receive my e-mails without being limited to 140-160 characters as appears to be the case with text messaging services only. I also want a phone that I can use outside of the US, that has a good size screen for reading my e-mails, has voice recognition for dialing outgoing calls(and reading e-mails back to me would also be great but less important). I would like a dual band or triband phone and probably a dual mode phone as well for those areas that don't have any digital. What do you all recommend? I can't decide between all of the overwhelming choices- AT&T, NEXTEL, Verizon, Cingular, VoiceStream, and Sprint PCS. I'm beyond lost and need some real good advice. Everyone tells me something different and I don't know what to think. GSM, TDMA, iDEN, TDMA, SMS, AMPS, etc. PLEASE HELP!!!!!!