Styling aside, there is little to chose between all the different V6 models from a performance/reliability viewpoint. The extra cc of the 2.6 and 3.2 is easily offset by the lower compression ratio.
GayBoyGixer makes a valid point about the 2.6/3.2 more likely to be lower miles, but then they are more likely to have been subjected to the daft 20k service interval. 3.2 obviously isn't available with a manual box in retail form.
Bodywork, obviously the FL is newer, so should be in better condition, but also seems to be better protected against rust.
Mechanically, virtuall identical, so nothing to chose there.
Styling is purely personal. The back of a facelift has grown on me (but it does need that lip spoiler), but the front hasn't. The interior layout, I remain on the fence, but the interior finish is awful on the FL.