Longear vs Dollar

What is the difference between Longear and Dollar sunfish in general?

Longear, larger, wider range, no spots on their black ear.
Dollar, smaller, often with blueish markings on the ear. More coastal and along the Mississippi.

Habitat is important. Dollars, like Casper noted, are more coastal and found in swampier habitats. Longears, while they can certainly be found in slower flowing water, are typically stream dwelling in my experience. Given the fact that they are so widespread and variable I am certain there are exceptions to this.

Male courtship behavior different at least with sympatric populations of the Missouri Boot Heel. Longear spin-up and lead in a horizontal pattern while dollars do a lot of vertical dancing in their display as they try to entice female to approach nest site. Not a general difference but something major is going on with respect to larval behavior. The difference I bet is biggest reason one species replaces other when habitat changes. Not all longear or even dollars are the same so do not over generalize. I think OP's original question needs to be qualified to compare specific populations of both, particularly those likely to be encountered by the OP.