What is better for gaming? If the option of soft press isn't really needed in most games I'd probably put hard and soft in one tact with the transistor method but I'm not sure how many games use just the soft press
The first one that come on my mind is mario sunshine, when you soft press, you spray water while walking, but you hard press you spray water without moving. I don't know for other games...
I don't think you'd have much trouble stacking two buttons on top of each other if you use the right kind. You could even purchase or find a dual tact switch, like the ones in some cameras, which are two switches in one.