The Asian 6497 is closer to gen in terms of bph. The more widely availably swiss 6497-1 (relative to other swiss versions) runs at a slower bph. If you want closest to gen, it's the high beat swiss 6497-2. But no one offers that these days. Used to come in the old EL PAMs with the old bridges, but now no one offers them.
Both swiss and asian 6497 will run just as good once serviced. Some asian movements, if you're lucky, will get more than 52hr power reserve due to longer spring barrel. If you want more than 60hr power reserve, bring it to your watchmaker and have him replace the standard spring barrel with a longer one.
Most master modders out there prefer to build using the asian one. It's cheap as hell, same built quality as swiss, and performs as good if not better in most cases after servicing.
If you'd like to know whether yours is swiss or asian:
1. Look at the shock absorber for the balance wheel (most recent swiss has the novodiac, asians copy the incabloc - the one with the two half-circles).
2. Get a loupe, look at the plate underneath the balance wheel close to the outer perimeter, you should see an ETA stamp there if it's swiss.