I will not delve completly into the answer you need, as that is quite a large discussion. In the realm of the two twins you have mentioned, I have a fair amount of time in each. I ferried a Crusader from Canada to the UK decades ago, A nice aircraft though definiately with its pros and cons, like any aircraft. If you have specific questions, feel free to PM me. There is one based in Bremerhaven Germany, which I see flying frequently when I am there, perhaps you can contact that owner. I'll get more info on that one if you need to find it.
The 310 is wonderful for the role for which it was designed, though they are getting old now, and there are very costly maintenance requirments imposed upon them, of which you should be aware. Again, if you have specific questions PM me.
Unless you need the multi engine capability for specific safety, I'd stick with the singles. a C210 is good, but for what you want to carry, you should also consider the C182RG. I've flown both, and certainly prefer the 182RG for several reasons, of you're not trying to actually carry six people.
Pilot DAR