Here's how I stand....
2003 Tahoe 4x4 - No Studs.
2009 BMW X5 - Studded Hakks
2010 STI - triple studded Hakks
1994 4Runner - No Studs

I run aggressive tires on the tahoe and the 4runner. BF Goodies AT on the tahoe, Destination MT's on the runner. I've never been stuck, and neither one really slide.

On the STI and the X5, I run performance Z rated tires. So in the winter I swap them out for something with a bit more bite.

 

one thing i also figured out this winter driving around is ice grips differently at 30 than at -7. without siping, but with studs i am all over the place on ice @30 degrees. But at 10 or below the ice gets almost tacky. I had no problem what so ever when it was that cold, it was like driving on dry pavement. anyone else have this experience?

 

Alex, I completely agree.

 

Iam running studded winter tires that are close to stock size. They work really well as the roads here are icy all winter long. They work well enough (especially in 4wd) for deep snow that there is no point in running my all terrains in the winter. The all terrains have very little traction when it gets cold. Soft tires (sipped) make a much bigger difference in winter then studs though at least around here.