An internal SD/FF has better quality indeed, but not really because of the shorter paths (though this is true to an extent). What it's doing is using the digital signals from the chips, rather than redigitising the analogue output on the monitor port. Then again, the difference isn't really that great, and if you feel you'll need it for another Amiga, then go for the external type. Also, some internal units can have trouble with overheating in the confined space in the desktop cosing. I've one in a tower so I haven't had any trouble with it, but best to ask around about a particular model.
