Please explain if this doesn't make sense. Miner Bob is the fastest miner on earth and the blocksize limit has been reached. He collects as many txs sorted from highest to lowest and tries to solve his block. Miner Alice is twice as slow as miner bob. She collects txs with fees sorted from highest to lowest, but she tries not to include fees so high that Bob will be likely to have included them in his block. She begins mining. Bob finishes his block before Alice finishes hers. Bob's block has higher fees in it and they were confirmed faster than Alice's. Hence, those sending tx's with lower fees know that people like Alice are more likely to get them and can expect slightly longer wait times. Again this only happens if Bob has a reason not to include low fees - the blocksize limit forces him to choose only the highest fees. Does that make sense?