Steve Koski, IDPA champion, engineer, and occasional visitor to the GunDudes podcast, has published a report on the differences between a Gen 3 Glock 17 and a Gen 4 Glock 17.
His report tears down the two generations of Gloc 17's as only an engineer could do. It delves into the minutiae of the differences. Steve also present his perceptions of the differences in terms of shooting.
If you have been wondering whether to stick with the Gen 3 or move up to the Gen 4, this report is well worth a read.