My opinion on the S30 vs P5 -- no comparison!! I considered the P5 before buying an S30, and the S30 is a much better camera in many ways. Here are my reasons for going with the S30:
Canon lenses are just better then Sonys (if you want a Sony, buy one with a CZ lens -- i.e. S75 or better)
Compactflash vs. memorystick-- much cheaper per MB and available in much larger sizes
LOT more manual control options than the p5 (p5
Greater ISO equivalency range (50-800 vs. 100-400)
More preset white balance options
Much shorter cycle time than p5 (1.9sec. vs 4.7-8.1sec. for large JPEGs according to imaging-resource.com)
Much shorter auto-focus shutter lag (0.75sec. vs. 1.5sec according to imaging-resource.com)
And I don't think the p5 has a real continuous mode (only 2 shots from what I remember), but not sure on this.
I could go on. But these are the major ones.