Well the title says it all actually.
But I need this for my GUI functionality, I want to make everything resolution independent.
Don’t worry I won’t calculate it every OnGUI frame, I got that covered 
It goes against my feeling to think that the more number multiplication will be as cheap as the simple one. But then again, they are both based on 32 bit floats right?
Thank you for your time!
They are both the same speed.
As you say yourself, both are 32bits, no matter what number you specify.
Even if you spefify a much to large number like 0.4234783217483174907381275178231, it will still be the same speed. The reason is that those numbers are constants and therefore the compiler will truncate them to fit the 32bits.
This will take place at compile time and therefore doesn’t affect the execution speed of you game at all.