Bigger diameter, yes - but a bigger footprint overall depends on whether you are driving more on ice (wider good) or on snow and slush (wider bad).  

Here, where snow and slush are much more the problem, tire shops routine recommend going -1 in size for wide-track tires on newer cars - our Toyota Matrix, for example, which has 205/55R16 summer tires, should have 195/65R15 winter tires (which do clear the disc brakes).  Wider just makes you slide in the snow, where narrower digs in.

James
Ottawa, ON

> Date: Thu, 3 Dec 2015 10:14:22 -0700
> From: OlRivrRat@COMCAST.NET
> Subject: Re: Snow Tire Recommendation
> To: vanagon@GERRY.VANAGON.COM
> 
>         In most SlipperySituations the Bigger the FootPrint the Better ~ So go with the 
> 
> Biggest Tire you feel comfortable running on your Van ~
> 
>         Larger Diameter has the ExtraAdvantage that it Puts Less Torque ToTheGround
> 
> which Translates to Harder To Spin ~ & a Longer LeverArm for your Brakes to DealWith
> 
> which Translates to Harder to LockUp ~
> 
>         Those Gen'Grab' AT2s are a Great AllAround Choice ~ A friend of mine & I do a lot
> 
> of Vanagon Rehab & that is Usually the Tire of Choice ~
> 
> 
> On 3 Dec , 2015, at 9:00 AM, Dan N wrote:
> 
> > I don't live in snowy/icy area but I have 14" General AT2 tires. They are
> > studdable (pre-drilled holes)
> > 
> > http://www.tirerack.com/winter/tech/techpage.jsp?techid=151