Move 4 to 5 or 4 to 7

Hi there I'm trying to decide wether to upgrade from 4 to 5 or 4 to 7 (SE) If you get any info I would be most interested. If I find any out I'll contact you. What I have found so far is that 7 has a new cost based optimiser that can speed up queries : more sophisticated than the old update statistics in that it takes into account data distribution etc 7 will also be supported for longer than 5 (or 4 in my case which is currently unsupported by informix) Also moving directly to 7 means you don't have to migrate via 5 & 6 etc. I hope this useful, If you get any better info please let me know. Many thanks