Some of those boots are just for show and aren't really comfortable for the dogs to wear because they are so "clunky" and can come off easily. When we found out we would be going to Alaska this winter I wrote to Alaska Yorkie to see what he recommends I buy for my girls and this is what he recommended;
To wear on cold days, not wet days,
http://www.dogbooties.com/products/fleecebooties.html
To wear on super cold days even wet days,
http://www.jbpet.com/index.php?main_...roducts_id=540
You could let the dog get use to wearing the fleece ones first, inside as well as out as long as it isn't wet out, then on cold days they can wear the boots and even super cold and icy days you can even put the fleece booties on first and the boots over that.