I have a friend who designed a game a few years back (but hasn't really gotten around to publishing it). He has a conflict resolution mechanic that utilizes either cards or dice (but not both, ala Savage Worlds). For example, Player A can use either a deck of playing cards or rolling several die and the same goes for Player B. It's even possible for Player A to be using playing cards while Player B is rolling dice.
So here's my question: is using such a mechanic worth it in your opinion?
I mean on one hand, it's a nice gimmick. Some people trust their luck more with dice while others with cards. On the other hand, aside from the problem of probabilities, the system is less streamlined that way. It could even be a marketing problem as it'll be the game that everyone will label as the "dice or card" system instead of its other core assets (unless you think such a label leads to a greater overall benefit).