A bondsman will make sure (if you pay him or her) that you're released ASAP after being booked at the jail.
A defense attorney works with you after arrest to minimize the damage caused by the arrest, and hopefully for you helps you avoid jail or prison.
Yours is a chicken or the egg type question.
You need both, unless you're loaded with loot.
In the loaded with loot case, you'll only need the lawyer and a trusted relative or friend with access to lots of loot to bail you out.