Just from observation, most sport, scale, and 3D pilots fly with thumbs. Every helicopter pilot I've ever seen flies with thumbs. The majority of pattern pilots fly with the pinch method. Both have their benefits. The thumb method allows larger movements faster, which is needed with 3D or helicopter flying. The pinch method gives you more precision, and it's easier to feel if you are accidentally feeding in an unintended control command like rolling while pulling up in a loop. Both give you plenty of access to your switches, and both can take you to a very high level of flying skill if you work at it.