There is more flexibility & navigational abilities running with an Mp3/Wav etc. ...especially using a Laptop for seamless multitasking on stage....plus editing is a cinch regarding cut/paste/loop/chain/Eq/efx, etc etc by doing it on your Pc editing programs like Acid pro,Cubase etc etc ... you would still play the SMF thru your KB into your recording program to convert to Mp3 format.
There is nothing that makes it easier then using a Laptop setup correctly & an arranger KB to mix it up on stage for performance or backup..