If you are grouping all the LG Optimus models together, then we'd have to group all the Samsung Galaxy models together. There's something like 13 models of them too.
That aside, I don't have any experience with the LG phones at all, so I will have to defer to your experience, Kolosus. I was just foaming at the mouth for the dual core 1GHz CPU, 8MP camera with flash, and front facing camera. Those are 3 things I just can't get from my Prevail.
On the subject of the Prevail. I think it is the greatest little phone I've ever owned to date. It is wonderfully supported by Samgsung/Boost Mobile (the twin Brother at Straight Talk is the Samsung Galaxy Precedent -- still on Froyo with NO expectation of ever receiving an upgrade!) and once I got a2sd installed, the issue of its tiny onboard memory is no longer a hurdle to using it.
Long live my Prevail!