Which is which?

They are alike in that they are both basic combination harness- to booster forward facing seats, but they have some fairly specific differences. Like, the fact that the top slots on the maestro are about 2 full inches higher, which for many kids, means the maestro will fit a slim child up to 2 YEARS longer in the harness than the gen 65. The gen 65 has the higher weight limit(65 vs 50 lbs), but slots that are much shorter...so...for a child with a longer torso and light to average body type, the maestro is probably a better choice, and for a child who is short, or has a short torso, but is very heavy and needs the extra weight limit, then the gen 65 might be the better choice.
The other difference is how they fit as boosters. The gen 65 is known to not always position the lap belt correctly, which could lead to stomach injuries in some children. The maestro tends to fit better in the lap area, but because the headrest is not adjustable, taller kids can't really use it, and the booster portion is outgrown almost at the same time as the harness, so it's not a very functional booster really.

All seats have pros and cons. I'm happy you found a seat that is currently meeting your needs. Remember, the best seat is always the one that fits your child, your vehicle, your budget, and that you use correctly every single ride Welcome.