Using a single tact switch will be the easiest, but you don't get full compatibility. Games like Super Mario Sunshine will not work correctly
Dual tact will be a bit harder, but you will get basically full compatibility (Only issue is you don't have the full range of movement of a real R/L button). Games like Super Mario Sunshine will work just fine.
Full analog R/L will be much harder, but you get full compatibility. You'll have issues making them fit inside of the case and mounting them, they also will add thickness in general.