I love these questions, and the answers (and arguments) they elicit. First, of course, there is the technical side of the question and Rocky nailed it. While there are techical differences in case capacity which leads to both theoretical and actual performance differences, they are slight as to be unseen in the field or on the range.
Secondly, there is the practical side. The truth of the matter is, from a users standpoint, the difference between the cartriges discussed is virtually zero in terms of accuracy and power. In both cases, 220 vs 22-250 and .308 vs 30-06 the differences are so small as to be absolutely unnoticed by either the shooter; or the game taken by any of the calibres currently compared.
As a side, I recomend reading this article from another site. It is one of the best pratical answers I have seen to a whole series of questions regarding cartrige selection, bullet weight, velocity, sighting recomendations etc.
http://www.kifaru.net/posimag.htm
Isn't it great that we, as a hunting and shooting group, can have such strong opinions on matters so small:--)