Oh i didn't see where he wanted more grilling space? Anyways he probably has no idea about the mini. I'd take mine over a full size grill any day of the week and twice on Tuesdays.
For smoking area he'll have the same cooking area considering loading up charcoal via snake method or on one side. Also peeps aint NO WAY i'd choose to smoke a brisket on a kettle personally....not saying it can't be done.
On the other side of the coin the mini is a way better smoker/cooker than kettle smoking could ever be using a fraction of the fuel.
I'd add the big kettle is good to have, it just wouldn't be my first purchase especially since he already has a SJ.