The weather in the Mediterranean in October is a little more unpredictable than earlier on in the year. Yes, you can hit storms and yes, smaller ships do tend to move about a little more that the bigger ones. Choppy is ok and all the ships around will cope with that well when the swell starts to get upish even the very large ones are known to do some unusual manoeuvres and are not immune to rocking and rolling and there is often more water in their pools to slop around and over the side. So ever time you go to sea you are liable to be exposed to movement. Personally I love the smaller ships as they often ride the weather well. I am not sure whether your uncertainty is based on past experience or if you just think you won't like extra movement. 40,000 tons is a reasonably sized ship, it is not like a cork in the water, so I would say try it out. Neil.
A couple of years ago, we had 2 weeks on Thomson Destiny, starting on the 6th October.The med was like a mill pond and although some showers over night in some ports, it was very warm and we spent the last day, 20th oct, sunbathing. the 2 weeks prior to ours had been cold, wet and stormy!
If you Google weather underground it brings up a site where you can hit the history button, choose a destination, input your dates, choose a year and it will give you the weather forecast from day to day.