Preferable type for process' variables and GUI parameters?

I read som topic about costly to/from float conversions...

As all GUI variables are float, will it be more optimal to make all process' variables that involved in GUI float as well?

I know, that it will make memory footprint to grow, but on the other side float conversions wouldn't consume cpu cycles...

What is your recommendation?

My recommendation is to follow the rules of optimisation.