Hi firehead.

This is very simply, don't go anywhere near the Yamaha and buy the Roland.

The Yamaha only has 32 note Polyphony where the Roland has 128. For midi file playback you will exceed the limitations of the Yamaha and so the sounds will start to cut off.

So if you want your midi files to play back without any problems, go with the Roland. It has more than enough Polyphony and sound wise it's excellent value for money.

Regards
James