If I was going to invest in a single character for all around, it would be a genetic hands down.
For making zeny in instances, I prefer the RK because of the speed and the fact that you use almost no supplies, even with average gear.
I have to dig on Swordsman forums for that.
I have DB RK and it has the most number of pots/strawberries/ygg consumed among all my characters next to gene. Don't have have a god/mvp card tho....
Still amazed to find out that RK consumes less supply