Unfortunately if it's prevailing winds and landing to the west then it really doesn't matter which side, left gives you a better view of Tibury and Dartford

In the event it's an approach over the City landing to the east, both left and right have good views in clear sky, maybe left side slightly better as you bank over the Shard and look upriver towards Hyde Park. Of course you have an equal chance you'll pop out of the clouds at Excel and see nothing!