I just find it really interesting that you're buying a Vintage bike (presumably you don't own one right now) for the purpose of riding in L'Eroica. I suppose its become a popular enough ride to coax people into riding Vintage bikes for that purpose.

I suppose the main things to be concerned about aside from Proper Fit of the bicycle would be conforming to L'Eroica's rules for bicycles.

- Pre 1987
- Downtube Shifters
- No routing of brake cables through the frame
- Pedals have Toe Clips w/Straps

either of those bikes fits the bill.
A Cinelli Supercorsa is a sweet ride. Just make sure it fits in with the rules for bicycles or you'll have a really nice, very expensive vintage bike that you can't ride in L'Eroica.