I thought the Kaplan was good for biology and chemistry. Pretty overkill in those subjects actually. Useless for reading and math, although they give some good test-taking tips for those subjects.
I never used Collin's, but I've heard very good things about it. I've seen people suggest focusing on Collin's and only use Kaplan's if you have time.
Do very very well in those summer chemistry classes! Kill them and try to get A's. A key to doing great on the PCAT is learning the material well in undergrad courses so that you're just reviewing for the PCAT. I had a strong background in bio & chem from undergrad and using just Kaplan I was able to score 99's on those sections.
Taking practice tests is important, too. I found the Kaplan tests harder than the actual PCAT while Pearson's practice tests were pretty spot on in terms of difficulty. Take one as a diagnostic to see how you're doing in the subjects and to identify things you needa work on. Try taking them under timed conditions, too.