Both the Gen 3 and Gen 4 are good choices. The grip options for the Gen 4 may suit some better; I'm great with a Gen 3 due to my hand size. The smallest Gen 4 will handle smaller hands than a Gen 3. The dual recoil spring issues have largely been "upgraded" away by Glock. Part for a Gen 3 are still more readily available. You can use a Gen 4 mag in a Gen 3, but not the reverse.