You're comparing the wrong things. Negotiating power ultimately only comes from having other options. I could choose other apartments or the landlord could choose other tenants. The balance obviously depends on the individual market, but I think it's much closer to parity.

> It's much more expensive for me in time and money to move than it is for a landlord turn over a new unit.

I'm not so sure about this, either. It's a pain for landlords to move new tenants in, too. Most would prefer to keep good tenants around as long as possible.