External blu-ray reader? USB 3.0?

I'm looking to buy an external blu-ray reader. I would like the drive to also function as a CD/DVD writer as well. I do not need blu-ray write capability, although I don't know if you can get a blu-ray reader that is also a CD/DVD writer. Even if you can, is it really that much cheaper than getting a straight up blu-ray burner?

Also, I would like to have the drive be USB 3.0 compatible, if possible. How much of an advantage is USB 3.0 vs 2.0 when actually using the blu-ray reading functionality?

Thanks,
Matt