The only way to settle this is with numbers.
Darren Lewis accumulated 10.5 bWAR and 8.1 fWAR in 1354 games, 4654 PA's
Bradley has 12.3 bWAR and 11.6 fWAR in 688 games, 2559 PA's (a little over half as many as Lewis)
It's fair to say that Bradley is roughly twice as valuable as Lewis was.