I hope you enjoy this place as much as I do.
That's a lovely Breguet you are looking at. It's been out of production for some time, but if you google it, you'll find a few posts here on WPS about it.
One of those threads discusses the movements. The earlier one is said to be a JLC movement, while the latter is an F. Piguet, a brand that would become the movement maker for Breguet and its sister brand Blancpain under Swatchgroup (along with Lemania).
I like F.Piguet movements, so I would go with that one. The F.Piguet is perhaps jeweled a bit more robustly, however, I don't think there is a real advantage the way you seem to be trying to compare the two. You would be well advised to rather consider the quality of the watch in front of you in terms of condition, as well as simply the trustworthiness of the seller. You may have heard the idea "buy the seller" and this is good advice.
If you do buy a Breguet, I think you'll enjoy it a lot. Remember to take a few pictures and share them with us here!