The Atalanta is SUPPOSED to weigh 2 tons or roughly 2000kg. Of course it depends upon how much kit you carry, and you need to add the weight of the trailer. I suspect that few Atalanta’s actually weigh that little – but that is pure speculation. I do know about Calista though. The titania is also SUPPOSED to weigh 2 tons. However it is difficult to see how that was ever the case with the big engine and extra accomodation. I did have her on a weigh bridge when she was on the trailer I sold to John. I was told she weighed just over 3 tons. That was with empty fuel and water tanks, and with normal cruising kit – but little food. That was why I went for a bigger trailer! When you contemplate long road journeys at moterway cruising speed (50mph) you really start to think about how suitable your trailer really is. Not that I want to give the impression that I sold John a problem – I didnt – It had taken Calista safely to the med twice. It is just that when I KNEW it was overloaded I could not ignore it.
So I thimk it depends on what you want to do with the trailer.
If you want to take it from storage to the water twice a year, and you can have it fairly empty for that task then I think a trailer capacity of 2.5 tons or say 3000 kg would be reasonable. I think that the boat has to be VERY empty to make this weight. So the light weight suspension units would be sufficient in this case.
On the other hand if you have some distance to travel, and you need to transport the boat with all its equipment in place (like I do on a long trip) then the heavier units would be better.
Since the difference in cost is minimal I would fit the heavier units. My reason is simply that the chances of overloading the suspension are reduced – I think the boat will inevitably have more kit on board than you expect when it is transported. However dont forget the tyres. What is the maximum weight permitted for the tyres on your trailer?