Well... if Smith DOES get 100+ PIM in the NHL, I'd agree he's the choice.
But big PIM in the NHL has trended down among defensemen in recent years.

NHL teams seem to be filling their 5th/6th defensemen these days with serviceable penalty-killers & shot-blockers, rather than goons.

Look at the number of 100+ PIM defensemen since 2005:

2011-2012: (3)
2010-2011: (6)
2009-2010: (5)
2008-2009: (14)
2007-2008: (15)
2006-2007: (23)
2005-2006: (22)

It's a pretty strange trend... but it certainly seems that most NHL teams prefer to have their 4th line forwards doing the fighting, perhaps.
Or maybe penalties have gone down as a whole... I don't know.

I do know that 100+ PIM sounds like a LOT for a kid coming up from the AHL. PK Subban pulled it off... but he takes a lot of stupid hooking/tripping penalties. From what I've seen, read - Brendan Smith isn't going to take those stupid penalties and I really doubt he's going to drop the mitts with the big-boys a lot in his first couple years.

I could be wrong... but there's definitely a PIM-trend there among NHL defensemen.