Verizon, Cinglar and Sprint all offer similar services at similar pricing. Look at their various plans to see if any of the minor features of one suits you better than the others, but the major features are essentially identical (but described with different words and matching hype)
Each provides coverage to about the same number of people nationwide, but there are minor differences in just where each has coverage. In any given location outside of the top 150-200 or so metropolitan areas, you may find that two of the three has coverage and th third does not. Go some other place and it will be a different two carriers serving the area. In other words, it depends on exactly where you travel. Quite afew of us have phones from two carriers so that the odds are that one always has service. If you get two separate phones with modest "minutes", it's about the same cost as one phone with a lot of minutes.
As for getting online (data services), Verizon & Sprint seem to have the best coverage and services. Cingular is behind but catching up.
Check out the
Internet By Cell Phone Yahoo Group, which is dedicated to this subject.