Great thread. Haven't even read every post yet. I have plenty of experience with both. Worlds of difference. Let me give you the cliff notes then expound.

If mostly road go narrower studded.

If mostly trail or thick soupy stuff go for width.

If saftey is primary concern definitely studded.

So... I love the performance and saftey of my 38mm studded. 99% of the time they're awesome.

The only time they're not awesome is in thick soupy, uneven snow such as tracked up unplowed roads or trails. They rock because they cut right through loose, powdery, slushy and even crusty snow and hook up with the ground underneath. Fatty's will spin all over the place, both front and rear making them unpredictable. Their only advantage is really uneven tracked up snow but such snow is really the exception.

BTW bigger diameter is ALWAYS better. 26" just don't get the traction and control in the snow.

In an ideal world I'd have three bikes or three wheelsets on hand for winter riding and commuting

1) standard road, semi slick 32-34 mm, for use 90% of the time.

2) studded 38mm, for gneral snowy day road riding, icey or just plain extreme cold days where black ice can just magically appear... Probably only a tiny percent of winter days but of extreme importance for saftey on the road in such circumstances.

3) a 29r or even better fatbike... The wider the better for big storm days, trails, fun. There is no such thing as to wide. 2.5" are way better then 2.1's but 3.5" and the new 4-4.5" are a whole mother ballgame.

In reality I have a surly cross check with dual wheelsets containing my favorite Conti Travel Contact 34mm on one and schwalbe snow studded 38mm on the other. Then I have a 29'r which I can't wait to get my 2.5" on this winter.

One day I will have a fatbike. I have ridden them fairly extensively. I just haven't been able to afford one yet.