I have never fired a BFR and probably never will.
That aside, buying something because it is all you can afford at the moment is always a mistake.
Every time you shoot it you will be thinking about the one you really wanted.
Take the money you have set aside for the BFR and use it as the down payment on the 500 that you really want. Then make the Lay-A-Way payments until it is yours.
I know in this day and age everyone want's things NOW, but patience pays off.
image courtesy of John Ross
Barrel length makes a difference but it depends on what you want to do