When playing games it would be very hard to tell the difference between a 5900x and 5800x. Unless you are doing professional tasks that need the extra cores the only reason to have 5900x for games is to inflate your epeen. Yes my epeen needed inflating I guess but I did not have a budget to stick too.
You will not be disappointed if you go with a 5800x.
You will not be disappointed if you go with a 5800x.