The early 520 is nice, but it would have to be dead mint before I'd consider parting with $600. The Pacer is a nice bike from what I've read, and it does have at least a passing resemblance to a vintage bike. For nearly equal money and as a newcomer to road bikes, the Pacer is the way I'd go.
Here's an '83 520 that I parted with last year, I would certainly have kept it if it fit me better.
