Can't speak for rotary from personal exp (only had a few trial lessons in some truly bottom end ones) but it's obvious that if you want the ultimate capability to fly from A to B no matter what the conditions are, and you have ba11s made of solid brass, not to mention disregard for rules, a helicopter will beat fixed wing anytime.
I see them flying under OVC002, in thunderstorms, in fog, in fact anytime anywhere. If the pilot loses his nerve, or comes up against a solid wall of fog, he can just put it down somewhere, go for a wee, and eat his packed lunch.
Obviously it's also a good way to get killed but I think that a clever and very good rotary pilot will have a much greater all-weather mission capability than an equally clever fixed wing pilot.
To get comparable ability to go anywhere in a fixed wing one would need to be doing seriously hairy DIY instrument approaches on the GPS, and then you still have to find a runway.
If I wanted to be able to travel around the UK in all weather (say, had a business where I was on a constant call-out and the work was of very high value) I would buy a turbine helicopter, probably a Gazelle, and get a military instructor to train me to fly it. Or something newer with an autopilot - I believe there are some American single engine turbine helis that have an AP even though very few singles are approved for IFR (of course this is entirely N-reg context). A friend of mine sells a lot of this stuff.
I don't think my IFR-navigation comparison was entirely irrelevant - helicopters must be a very good example of a case where most pilots have to fly under VFR, and for basic safety reasons have to remain VMC, but I am sure all but the most hardened part-timers will be using GPS. Whereas in fixed-wing flight there is a large community which regards that as doing a pact with the devil.