The main difference I can see is if you send via email, the 5 MB counts against total inbox space. That's not a concern with gmail, or another "large" service, but many other commercial accounts only have 5 MB or 10 MB limits. Given a choice, I'd set up an ftp or some other download method. Then again, maybe I'm too old-school (i.e. five years ago) in my thinking...
Actually the most striking difference is that email providers cut upload speeds to a few kilo-BITS-per second. So, a 5 MegaBYTE file file would take a lot of time to upload.
PS: 8 BITS = 1 BYTE
And thanks again, jdm, for the other link!