I have a G6, and it has blown my mind in terms of what a mini-slim is capable of, especially if you have the LR cartos.
Surprisingly my biggest gripe with it is knowing when the cartos are empty. Halo says the vapor production will greatly decrease, and you'll get a slight burnt taste. However because of their new design they don't really burn the way carto filling usually does so I was really thrown off because when it got real low the flavor really changes, but not burnt tasting, and the vapor stays strong. I know they are about out so I won't push it any further, just pluck the top off and drip some drops into them, but I don't know, I actually prefer to get that burnt taste as its more noticeable to me.
As for the Vea, I haven't used one but I think my friend is ordering one so I'm going to "borrow" it from him to try it out for a day. They have a bigger battery (I don't know the charge time on it though) which is nice, but it is noticeably thicker and that is the only reason I wound up choosing the G6 over the Vea. I believe the Vea is a 510 which means there is more you'll be able to grab for it right off the bat.