SeenItAll -
The main difference between your hurricane hunters and commercial aircraft penetrating severe weather is.....PASSENGERS. The airframe will normally withstand much more than the pasengers can endure. And, the pilots and crew of those hurricane hunter aircraft are strapped in, not wondering about the cabin or failing to "keep their seat belt fastened" even while seated !
Also, the convective forces are far greater in a thunderstorm, I believe, than in a hurricane. And, the imbedded thunderstorms within any hurricane are avoided I'm sure by those aircraft.