Sorry for the very very late reply! Work has been super busy and I simply hadn't been perusing PF as much of late.. I'm not sure if you still need an answer!
But just to share, the Bal Velo is definitely heavier due to the studs. The PS1 on the other hand, is relatively light-weight - which always makes me paranoid the seams will come undone each time I carry too much! But it's actually been holding very well~~ In any case, if it's too heavy to carry you probably won't want to lunge it around for too long!!
Also, because of the weight issue, I actually hadn't been using the Bal Velo for some months now, though I still love the darling because of its squishyness. Whereas my PS1 is my go-to bag every other day. =)
Hope that helps! =))