Hi Bas, in answer to your question, yes bigger bikes are better able to cope with the demands of motorway cruising. Generally the larger bikes are designed to deliver the power at lower revs and are therefore more economical at motorway speeds with the added advantage of more power if the need arises to get you out of trouble without over stressing the engine.
Bigger bikes also tend to be heavier with a lower centre of gravity which makes them more stable. Depending on thet type of machine you choose, the riding position is also improved. If you opt for a tourer, distance riding is more comfortable than if you had gone for a sports bike.
All bikes are subject to the effects of side winds and buffeting, however a bike with a fairing will help to deflect these forces around the rider whereas an unfaired or 'naked' bike will subject the rider to the full force of the airflow and at higher speeds, this can be considerable.
The best advice would be to arrange a test ride with a bigger bike if your licence will allow it (some new riders are restricted to 66bhp). Having tried a few differnt types of bike, decide which one best suits your needs and riding style.
I hope this information helps