Such a question leaves a lot of options to be considered.....
IMHO..........
in general the larger MRs, when properly designed and configured tend to be more stable in windy conditions. The same seems to apply to RC Helis and RC fixed wing planes from what I have seen.
1) Keep in mind that the NAZA controllers are designed to handle MR airframes with motor arms not longer than 650 mm (whereas the WKM and A2 are able to handle larger airframes and more configurations)
2) eCalc for Multirotors can do a lot of the design grunt work for you but at the end of the day, if the chosen motors do not have the necessary torque/speed characteristics for larger, heavier MRs, you will not be able to dial out the consistent airframe wobble that can occur. Such situations require a deeper level engineering design analysis.... in general that can be resolved by using more powerful motors...... prop sizing and pitch also playing a roll but to a lesser extent.
I live in Florida, and we pretty much have winds every day. I have an F450 set up for AP. Given all things equal would it be more stable in the wind if I were to extend the arms to 550? Is a hex more stable? Same question is a 650 hex more or less stable in the wind than a 550 hex?
Thanks,