Hi refault,
I'll try to lend some of my personal experience since I own both cans and have used both extensively in portable situations (ie. walking around city with busy streets, trains, buses.. as well as in uni classes, libraries). I'll list them in basic catergories that I consider important for portable usage.
Isolation:
The SR60's really do have a serious problem with sound leakage as others here have said. It's as much of a problem with you hearing outside noises as people around you (especially trains) having to hear what you are listening to.
If you want isolation, the V6's are the way to go, being both closed and circum-aural, the exact opposite of the SR60's (open and sitting 'on top' of your ear). Sound is blocked very well from outside noises, and there is hardly any chance for even the person sitting next to you to hear anything from your phones (unless the volume were to be ear-spittingly loud
)
Comfort:
IMO, the comfort of the V6's wins hands down over the SR60's. Because the Grados rest directly on your ears the friction and pressure can lead to annoying aches after anything more than 1.5 hours use.
The V6's nicely padded, even the headband, and for me I can wear these without physical fatigue for many many hours. However, since they encompass the whole ear, the V6's can get hot and even sweaty. Look up the Beyer-pad mods that many V6 owners have tried that remedy this problem.
Sound:
Because you said you plan to use either to listen to electronic music, I'll try to simply pick out the characteristics of each phone I've noticed in relation to the electronic stuff I listen to:-
Mid-range bass on SR60's in more apparent than V6's (meaning: more 'thump'? definitely more 'physical kick' from bass heavy tracks)
V6's have deeper bass than SR60's (meaning: I heard bass that I didn't realise was there before in the music - I had the SR60's for about a year and a half before the V6's)
Soundstage is wider, "airier" and more realistic in the SR60's than V6's (personal preference I guess, because soundstage may or may not be important to you for electronic music. I personally don't mind either.)
Overall sound generalisation: The V6's are clear and extremely defined; the SR60's are also very defined but warmer.
Hmm... Perhaps the best way I could describe/compare the two is: the SR60's are to the V6's what incandescent lights are to fluorescent lights respectively.
Build Quality:
The construction of the SR60's is very simple and spartan. More plastic than metal. I like them because the ear cups can swivel, allowing me to lie them flat and therefore saving space in my satchel bag when I go out. The cords are very thick, almost inflexible. I have a feeling they will last a very long time if you take care of them enough. I wouldn't chuck them around though.
The V6's are ruggedly built with much more metal/padding than plastic. I could chuck the V6's at my fish tank and they'll be fine. I wouldn't actually chuck them at my fish tank though. They conveniently fold up into themselves, but even so they're not as flat the SR60's so ultimately they take up more space in my bag.
Ultimately I love both cans just as much, but since acquiring the Sony V6's the SR60's haven't left my house.
Hope this helps a bit!
Cheers,
Pat.