Just back from Mull where I picked up a 10 year old Ledaig and a 12 year old Tobermory which are very different whiskies. I also got a 14 yr old Oban on the ferry for something in between. Should keep ...
Speyside is the obvious suggestion but I would add if you have a personal preference for a particular whisky or style like say Islay that is going to be perhaps a more enjoyable destination/trip.