Hi mikeyw, welcome to the forum :D
I've just been writing a massive essay about swapping my Riff Raffs and MQs over on a new thread
http://bareknucklepickups.co.uk/forum/index.php?topic=14098.0.
I've not tried the Stormy Mondays, but I pretty much agree with what Twinfan and Tom say. I think the MQs are an acquired taste, but as I've just found, it also depends on the guitar itself.
My Epi SG is mahogany. It's not a particularly bright or resonant guitar.
My Gibson Explorer is also mahogany, but it's a lot heavier, it's darker sounding and is much more resonant accoustically.
I liked the MQs in the SG, but I now know I found them a little too aggressive for me in that guitar. They are doing a superb job in the Explorer now, where the Riff Raffs were coming across a bit weedy when compared to the other guitars.
The Riff Raffs are now back in the SG (which they were bought for originally). If it was the only guitar I had, I would be very happy with it, it does crisp 70s rock - I've been playing Bonn-era AC/DC and 70s Ted Nugent on it today. It also does bluesy, which is where my main interests are at the moment.
My gut feeling is that you probably want Riff Raffs because of the "classic rock", but Twinfan's right, they might seem a little "cold" for blues - but I believe it depends on the circumstances. How clean a sound do you like using for bluesy stuff? The cleaner you want to get, the more you'd notice the "coldness". If you want to be playing like John Lee Hooker, for example, thick, slightly breaking up, you'd want MQs. But if you want a biting bluesy sound like 70s rockers used, I reckon you'd be fine (eg Angus on The Jack on If you want blood - that's where I started on the blues... long time ago now...), I was a big Rory Gallagher fan as well, and although I've got a Strat and Tele to cater for that sort of thing, my SG with Riff Raffs does Rory-type blues quite happily.