Love love love the Stubben EZ control bits. I have the loose and the D ring versions. Pretty gentle bits but the links lock in place if the horse leans on the bit. Hard to explain on her but go check one out of you can!
If you're training, you want the horse to respond well to a mild bit before putting anything else in his mouth. I second the French link. The extra joints is usually more comfortable for a horse.
I love love love the JP Korsteel Hunter Dee Ring Snaffle Bit with Copper Link. It's a bit more on the expensive side, but it has nice soft edges, is double jointed, and has a copper link witch most horses love, and are happy to push into.