I've owned (and sold) both of them.
Comparing them? There's a lot to write on that topic
especially because they're very different.
Keeping it short -
I guess you realize the Grado's are open and the AKG's are closed.
IMO the Grado's image more effectively
though it must be said that the K550's have a large soundstage
(and good imaging) for closed headphones.
Which are better for the genres you mentioned?
Matter of personal preference, I think.
The 325is's are brighter with more presence.
They're very dynamic and lively.
(BTW, I like the 225i's more because they sound quite
similar but lack a certain harshness in the highs
which many have noticed in the 325is's.)
The AKG's felt to me like a work in progress.
Not great at anything; not bad at anything.
They clamp lightly and if you position the earpads directly
over your ears - and they stay put in that position -
the K550's can sound very good. Detailed,
with solid reproduction throughout the spectrum.
except the bass where they seem lacking somehow.
The Grado's may not have more bass, but their sound
is very consistent within itself unlike the AKG's.
As you may be able to tell, neither of these are my
favorites in the price range but if I had to pick one I'd
pick the 325is's for clarity, detail, and more enjoyment
listening to them overall.
Hope this helps at least somewhat.
There's a big thread on the K550's which I think
you'll find helpful as it has so many different
views and perceptions from so many people.
