Sean would be a boring bachelor, IMO. He is very nice, has his priorities straight, wants badly to be married and have kids, but I saw no signs of wit or a spark really with him. Certainly nothing that could carry the show. We'd likely have another Ben fiasco if he were the lead.
Arie I think could do it, as he had some pretty funny little comments to the camera and seems to have a great sense of humour, is a great kisser, and really seems to try to focus on the lady he's with (rather than himself...take note, Ryan!) I can see him as The Bachelor, I'm just not sure I'd want him to be the lead. He should be fine on his own, as were Reid and Chris L.