Yes, different makes are different widths.
i.e. a Conti 245 may be narrower/wider than a Bridgestone 245, but within each brand (or model) they are comparable to each other.
Same goes for treadwear ratings, they mean nothing unless compared within the brand.
My Contis are listed as a 340 treadwear, but they are comparable to other brands in the 200's. As a sharp contrast, the stock Michelin Primacy are rated at 240 treadwear. No way are they stickier than the Contis!
Here are some pics of my Conti Extreme Contact DW in a 245/35R18 on a 9" wheel.
vs stock wheel & stock sized Michelin winter:
from inside the wheelwell:
outside view:
