Not sure if your concerns are warranted or rather if the hardside is a good solution for them.

Smells: Many hard-sided cases still have a textile lining. That will hold a smell.

Security: Why would anyone slit open the entire suitcase at its hardest do slit point, the shell? What a stupid thief. If it's a normal coil zipper (like both Pursuit and Winfield have), just pry it open with a ballpoint pen, then close it after pilfering. Much more elegant. If it's a toothed zipper (rare on hardsides), no such luck. But then one can always just cut around the zipper with a carpet knife. Very quick.

If it's a rigid frame case with a combination lock (Rimowa, some Samsonite and Delsey), this is a little more secure because a bit of brute force or extra time is needed to open it.

As for stuffing it in the overhead, a hardside can be better, provided the measures are small enough. The depth (smallest measure) is very often the deciding factor. If that is 8" you should be OK.

Till