I have found a burger press improves the texture and cook because you get a nice air pocket free even shaped burger.
Personally I add finely diced onion and roasted sweet pepper. I like to add sal, pepper, cumin and smoked paprika to the mix.
I agree with the comments on beef and cooking methods above. 20% fat an cook nice and hot don't flip too early or too often.
A burger press definitely helps get a consistent texture, thickness, cooking surface and size/shape.