Re: How would a 2x15 or 4x15 cab for lead guitar sound?
My favorite guitar cab is an Ampeg 2x15 bass cab designed for the B-25B amp from the '70's. The problem is that I don't like hauling it around for gigs. Not only do I have a small car now, but it's worse to carry around than an SVT cab. It is just as heavy, but has no casters, and only those crappy old '70's vinyl strap handles. I use it only for recording now, or if I had a gig at a big venue (like an outdoor place, or an indoor place that held thousands of people), I might go ahead and drag it out of storage to use it.
The tone is both bigger and tighter than any 4x12 cab I've used. But speaker selection says more about this than speaker size IME.
I also used to play my Ampeg V4 or a Mesa F50 through one or two modern SVT cabs: a 1x15 and a 2x10. Both worked great, and could, of course, also double as outstanding bass cabinets when needed (as that is what they were designed for).
In short, I love 15's for guitar, but I wouldn't regularly gig with a 2x15 or 4x15 cabinet unless I played to thousands of people for lots of money and had roadies. A 1x15 though, sure.