"viostor" or "vioscsi" Driver for Windows-7-64 ?

the difference between these two drivers is the following:
viostor (or virtio-blk): it is a basic block driver for the virtio disks
it is simple, but lacks some features

vioscsi (or virtio-scsi): it implements the scsi commands for the virtio disks
some features work only with this, for example discard

in general, i would rather use virtio-scsi (although redhat claims some performance loss)