Yes, they can be slow. This is a case-by-case thing. If you plan on ripping a LOT of optical disks you may want an internal drive. If you just want to archive a few disks like the OP, an external makes more sense to me.
You can get a USB 3.0 external drive, too, but they are more expensive. The Hitachi LG Data Storage GP96Y is supposed to be quite good, and works with phones, too.