
Just as a reference, to make things easier, I will refer to the Samsung Galaxy Precedent as the GP, and the LG Optimus Q as the Q.
1. Newer Version of Android (Gingerbread) Unlike the Galaxy Precedent, the Optimus Q comes preloaded with Android 2.3 Gingerbread, unlike the Precedent, which comes with 2.2.2 Froyo. Not only does it come with GB, but it is a near stock build of GB. Sure there may be Gingerbread ROMs for the Precedent, but it's just not the same.
2. Physical QWERTY KeyboardSay what you will about keyboards on a phone, a lot of people can not live without a keyboard on their phones, and the keyboard on this phone is darn near flawless.
3. Better Camera The Q has a slightly better camera than the GP. While the GP has a 2 MP camera, the Q has a 3.2 Megapixel camera. It also just takes a much better picture.
Examples:
LG Optimus Q:

Samsung Galaxy Precedent:

4. More RAM The OQ has a bit more RAM than the GP. The GP has 384 MB of RAM while the OQ has 512 MB of RAM.
5. Notification Light Finally, the OQ has a built-in notification light, which is great for people (like me) who don't always hear when you get a text.
If I missed any or if you feel like I should have added some other points let me know. I will be doing a full review of both devices soon since AC hasn't done one officially yet.