[crazzzzzyness]

I want to know which one has better bass. Also, is the MDRV55 bulky? If you have any suggestions for me, it has to be under $100, stylish and portable.

 

[Nooks]

I would recommend both for portable uses, as MDR-V55 is quite small for a headphone that covers your ears completely.  From listening to these in the stores, I wouldn't say that they are both bass heavy, but the ZX600 had a little bit more base than the V55.  V55's sound is more close to monitoring headphones and is very neutral sounding. 
 
Also, V55 has a lot less bulk compared to the old V700 line (which is the same thing as V55 except for the aesthetics), so I'm sure you can wear it around your neck all day and it wouldn't bother you.  It also folds up quite compactly. 
 
I always carry around my ATH-M50 around my neck with the earcups facing down, and that has not bothered me at all, so V55 with the same position would even be easier to carry as it is way smaller and lighter than the M50s. 
 
Enjoy your Sony cans!  Most of the time they have good sound for the money you spend.