"sweep" is basically the same as a normal transfer... both create a "standard" transaction that send bitcoins from one address to another.
"sweep" was effectively just a "shortcut" method that allowed you to bypass importing the keys first... you could enter the private key directly into the "sweep" dialog. It also automatically sends all the coins (doesn't create any change).
The downside to sweeping, is that you can't choose your fee... I think it just sends with the recommended fee (which could cost a LOT at the moment).
Also, if you're going to see your coins, probably don't bother sending from Electrum to Electrum... send them from Electrum to where you're going to sell them.