This is just my personal experience / opinion, but Ive had Glocks from gen 3 to gen 5. From my experience looking for competition upgrades, it is easier to find stuff for gen 3 and 4 than it is gen 5. Both of my competition glocks are gen 4's and couldnt be happier. I have a G35 set up for limited and a full race open G34 built by Carver Custom. I dont think you can go wrong with a Gen 4 but that is just my opinion.