Internal > External Burner Question

I am just wondering is there any difference between buying an internal burner and putting it external and buying it and having it internal. I know speeds is one issue but i will really only like to burn at 4x or 8x only no more.

Is there anything such as buffer problems to worry about or will it be ok.

Also which drives are good for making external. Would the Benq 1620 pro work ok. How about the NEC 3540.

Is firewire or USB 2 the better connection for a good 8x burn?

Thanks

External enclosures are fine. Just make sure you get the prolific chipset, and at least usb2.