I've seen a variety of helm locations on cats. There are dual helms at each side, there is the helm that sticks up through the aft deck roof and there is the big center helm up some stairs that sits above the salon.
Is one over the other considered a better design for long distance cruising? It would seem to me that being way up high is a longer pendulum, while in steep tight waves. I understand it won't move like a mono, but I'm asking about sea state that is moving the boat around.
I've also seen helms in the salon, but I've not seen line control in there. In rough weather, I assume one doesn't sail from in there.
Helm positions! Now you are intentionally being provocative! Better duck for cover after bringing up this topic, as it splits up catamaran owners like nothing other.
Before continuing, you missed a couple of options - forward cockpit helms, raised bulkhead helms looking through a dodger, lower bulkhead helms looking through the entire boat, and center helms in the middle of the "cabin" (different from the saloon helms you mention because they are the sole helm and sail controls are located there).
Personally, I think whatever floats one's boat is fine as regards to this. I do have my preference, and also highly dislike some - though I'm not sure any particular helm position would be a deal breaker for me if the rest of the boat was screaming to me.
They all have advantages and disadvantages, and owners of each will see these differently. I'm not going to be the one to start on this, but I think I can safely state a couple of aspects that everyone would agree to:
Helms in the aft cockpit take space from the cockpit.
Helms in the saloon take space from the saloon.
Helms in a forward cockpit can be wet and difficult to protect from the weather.
Helms in the aft corners can be difficult to protect from the weather and can be wet in rougher conditions.
Flybridge helms can cause difficult communication and are not easy to reach immediately if necessary. They are also difficult to protect from weather. The boom must be raised for them, and can be difficult to reach/work on.
Raised helms are an attempt to strike a balance among all, but can be somewhat difficult to protect from weather and take up a small amount of cockpit space (highly dependent on design).