Reaching back and forth behind the Windwards is great fun.
The abilirty to get to the islands with only the fuel bill for the refrigeration is also great.
The difference is in the volume of the boat , sail boats can not be beach balls , and the fact that on most sail boats you live below , in the hull , on many motorboats the best accommodation is above deck level.
Sail does very well offshore , 1 in 1000 power boats are built to cross oceans .
IF cruising costs are a prime concern the round trip with a solid 60s or 70s sail boat for a few years would be hard to beat.
As an auto pilot is needed for most marine motorists , a wind operated self steering gear is almost mandatory for an offshore sail vessel.
The Aries is my suggestion , as it is excellent in following seas.