Definitely ‘Persuasion’! But then I’m a total Austen geek so that’d probably be my standard answer no matter what the other option was.
‘To the Lighthouse’ is one of the only books I started and didn’t ever finish, which I’m quite ashamed about.
Having said that, last summer I stayed in Virginia Woolf’s summer-house in St Ives, which was fun because you could see The Lighthouse from the living room!
No offence to Persuasion - I love all of Jane Austen and I think either that or Sense and Sensibility are my favourites of her works - but I’m going to defend To the Lighthouse. I didn’t get beyond page 5 the first time I read it, but the second time I really enjoyed it. It’s beautifully written - I especially like the image comparing the stars to “platters of brightness” - with very carefully written characters, and a really interesting and I feel successful experiment in Modernist fiction. But I’d recommend Mrs Dalloway if it’s the first time you’ve ever read Virginia Woolf as that’s an easier read. I also like A Room of One’s Own.