Well not much to add as far as general differences that hasn’t already been stated. To the question of flying in turbulence or flying IFR well it depends.
First, generally you see helicopters react better to turbulence because of the rotor blades ability to flex. In moderate or greater you can see the tip path plane
flex up and down. Now, that doesn’t mean you won’t be displaced from attitude, altitude and heading. It’s just a more cushioned blow vs a jolt in an airplane. Obviously a lot on that depends on disk loading (lb / ft). Also in turbulence you get way more fishtailing because of the small vertical fins. Those vert fins and side plates are really only up to the task of offsetting torque in forward flight and assisting lateral trim. Doesn’t help much in turbulence.
As far as IFR flying, well unless you’re in the military or flying SPIFR EMS aircraft like H135,H145,A109,etc or larger aircraft such S76,S92,AW139, etc, you won’t be flying in actual. You might have an aircraft such as an R44 fully equipped as in part 91 instrumentation, but won’t be certified IAW part 27 requirements. The primary reason being, helicopters just aren’t statically stable enough to be used as an instrument platform. They also require more redundancy (dual pitot static / generators, etc). For instance, our company operates IFR H135s. In order to fly IFR, they have to have both stabilizing devices working (SAS) and a functional AP. All my IFR helo time is Army and while I didn’t have an AP, the Black Hawk was required to have both SAS and flight path stabilization (FPS) functioning. Of course I talk trash to the lazy 135 guys and that I used to fly in actual weather with both hands and feet without the luxury of an AP.
The other aspect of IFR flying in helos, is that they have a different set of IAPs for them. TERPS criteria is modified for Copter Approaches. Generally a copter approach has a higher glide path angle and obviously they use a slower speed on final. A lot of copter IAPs are proprietary ones that a company has made by a contractor. For instance, we have approaches set up all over at certain hospitals. Won’t get ya down super low, but they can pick up a patient that a VFR guy such as myself can’t get to.