If just the 500 Mbps pair are in use, you should see higher throughput between them. But if the 200 Mbps devices also become active, both pairs will share bandwidth and the 500 Mbps pair will slow down. So might not see the extra performance that you are paying for.
Note that bandwidth-sharing happens with multiple 200 Mbps (or 500 Mbps) devices, too. It's like any shared, medium. The more users, the less each user gets.