Hope you enjoyed your cruise Tim
Ionian Sea is calmer than the Aegean. Actualy in the summer months the Ionian is flat all the way from May to October and quite humid. Just a southerly breeze daily force 3-4 from 11am-3pm with a small chop and then flat again.
Aegean is different, VERY different in fact.
We usually have strong winds from mid July to mid/end August (is called MELTEMI). Force 5-7 starting at 8 am and ending at 6/7 pm on a daily basis. Waves can reach hights up to 2/2.5 mtrs at times but usualy they don't exceed 1-1.5 mtrs with surf and the distance between them is about 6/7 mtrs. (So the ideal boat to cruise in such conditions is between 6.5-7.5 mtrs LOA. - hence the KAIKI boats - a type of fishing boat used by fisherman). Nothing very serious but the wind and the waves with the surf and the sray make it quite uncomfortable if you go a long distance (which in any case is never more than 20 miles any way as you are on the next island).
However, this year it has been very nice in the Aegean. Apart from two weeks of force 7-10 in July the weather has been great. It has been recorded on the forecast to say sea state calm for the East Aegean!! and it was looking like a a lake all the way (still is).
You find more RIBs in the Aegean than in Ionian Sea for some reason.
RIBs here are quite popular (more than hard boats I believe) since the popular belief is that are much safer than the later - which they are any way
and RIBing is great. Is very different than it is in Ireland or in the UK or Germany, Swededn, Holland etc.
Boston Walers are quite popular too as they have been advertised here as unsinkable and quite a few people buy them.