In many ways, a larger boat is actually easier to sail than a smaller one. They react much more slowly, giving you more time to react. Their motion is much easier as well.
In the BVI, navigation is very easy. You can see most all the dangers, the few dangerous reefs are well marked, you get a briefing from the charter company before you depart, and the sailing is in "protected" waters. Further, good anchorages are many and are near to one another, so you can sail as much or as little as you please.
While the tradewinds can blow pretty hard, you'll get good experience sailing with reduced canvass, sometimes with just the genoa or a portion of it rolled out. You'll learn that the boat is very easy to manage if you don't have too much sail up.
Finally, if you or the charter company have any lingering doubts as to your competence, you can engage a professional skipper for the first day or two until you/he feel you're ready. It's a gentle way to learn and, for most people, a very good one.
Greece is more problematic, but doable. Unless you have a pressing reason for sailing there -- perhaps you really like Ouzo???? -- I'd do the first charter in the BVI where you can be assured of both an excellent learning experience, a great time, and a soft landing.
(been sailing the Virgins since 1969)