Level Progressions 5.5 vs. 7.5

One of the things I will be most interested in seeing, as I monitor and compare my 5.5 and 7.5 campaigns, is how level progressions match up.  Right now, after two sessions in the 7.5 campaign (although I've only posted one report thus far), the party average of accumulated AP is 477.  While attributes have been raised by everyone thus far, no one has gone up in level.  Compared to a 5.5 campaign, PCs would be half-way to second level now but would have experienced no attribute raises.  However, the fact that PCs started at various levels - one as high as 3rd level, as is the nature of 7.5 - complicates the issue.  While this once played havoc with my idea of how to balance a campaign, I now find the comparison between editions a fascinating case study.  We will see how it plays out long term.