You linked to a pair of BNC style triaxial bulkhead connectors. The main difference is that one has a slightly longer overall length. The only other difference is one (the short one) has the ground tab. The ground tab is just a slip on ring tab. If the connector will be used with a conductive metal box that tab isn't required as ground is ground. If the connector will be used with a non conductive plastic box then any ring type tab can be used as long as the diameter slips over the connector body.
Also per Sceadwian what is the application?
Ron