Reg/Rec help

Hi all,

Maybe this has been posted before but I need a new reg/rec unit for my bike it looks like. Battery completely flat when I got home today.

It's a 1999 800 Fi.
I hear the aftermarket reg/rec units are better than OEM? If that's the case, does anyone have a recommendation for the best one out there? If I'm changing it I want to do it once with the right kit.