Efile is for people who does other's tax returns as business. Efiler must register with CRA first, and have an Efiler ID/password to do tax returns.
Netfile is for people who prepare their own, family or friend's tax returns.
myTaxExpress has both netfile and efile version software, they work very similarly. Netfile and Efile software can also generate printable tax returns. The print can be used to paper filing to CRA.