Yes, John makes a good point about the boat that shuttles around Derwentwater so you can get on and off and hike and on and off and hike some more and on etc. It wasn't running when we were there in high winds a few springs ago. Another transit score for the Lake Dist. Don't know about Arthur's Roundtable, they didn't tell me about that, but Castlerigg Stone Circle is wonderful and, we know, a particular favorite of Ed's.
But if I were driving (and I'm not sure I will, it's harder for me in the UK than it should be) I think I'd go for North (or northern? above southern? whatever) Wales because of the variety and history. Note that John's last description of the joys of the Lake Dist mostly discussed the things it's near, not what's there. Great scenery, some history, Wordsworth and Beatrix Potter, OK. With Wales you get castles, seacoast, mountains (not just "fells"), scenic railways, interesting food, music, lots of history, and a whole different culture. But not, imho, great public transit.