Gen 3 without doubt. I have an overview knowledge of around 17,000+ Gen3s in use and it is really hard to fault them. Also very detailed knowledge of around 100 that are on a training cycle. They have had the bejesus shot out of them. Each revolver to SLP course is a minimum of 900 rounds per shooter, they get shot lots !!! Yes in the early days we kabooomed 20 !!! But that was all about cast projectiles and cleaning, a change to plated/jacketed saw that go away overnight. My personal 17 is also a Gen3 and and after toying with a Gen4 recently I will be buying ANOTEHR Gen3. They fit my hand well (again that is always personal) so no need to change.