I have the 960GB OWC card, so it's a bit slower than the 240 or 480GB versions. Still, this is way faster than the Apricorn Velocity (which basically just gives you a data 3 connector and as such is bandwidth constrained to Sata 3 speeds which top out around 500MB/s). The OWC card gets me 750MB/s reads and around 600MB/s real world. What's interesting is when you format the OWC with encryption, it only slows down to 400+MB/s, which is really good. It might do better with faster processors (I have a 2.66ghz 12 core 2010 MacPro).
So the Velocity is great in that it will get you out of the 250MB/sec limits of Sata 1.5, and into the 500mb/s range of sata III. The OWC will get you an extra 200mb/sec or so over sata III.
The OWC card has been solid for me, it boots/works without any drivers, but clearly they are putting out drivers to install to overcome bugs, so that means things are not perfect under all circumstances.
Also, the OWC card is oddly pricey in that its about 1500 for the 960gb version, and they sell a sata 1.5 drive for around 1100 with the same capacity. So $400 premium for the raid/pci card construct.
As always, YMMV