The 'e' is just to distinguish for us discussing which exchanges will hold which. The MGO in your ether address (you're accessing the address USING myetherwallet) is simply MGO because ether addresses can't hold WAVES assets...and vice versa.

The tokens are both MGO...just for purposes of distinguishing them when trading, one has the 'e'...they are the same asset and once the block swap tech releases there will be little to no risk for arbitrage messing with their prices