Is there a major sound difference? I have a 4 X 12 angled by Hartke. A buddy said that Randall only makes straight because of the tone diff? I don't know. I know a shop that is selling a Peavey Windsor 4 X 12 cab for $199 that is straight and was thinking of getting one.
There is a reason for them to be used in pair. The slant gives more of a wider and full projection think rythm, regular cab is more focused forward projection think single note focus.
I am sure that's how it sounds to some people. YJM plugs in only to regular cabs, slanted ones are just a stage prop. The way I think about it regular cabs "chorus" and launch forward the single note stuff, slanted is just better for the over all rythm projection into the vanue, I think its a must in heavy typa stuff where the songs are written around the guitar riffs.
Thats what I was talking about when I was talking about slanted, that's what most people think of when they say slanted cab, as its the most common form of a slant. The stuff like Laney Lionhear is not that common. I have a marshall JCM900 1960A i.e slanted 4X12.