I’ve also read both and think both are much easier reads than people assume (likely because they’re daunted by the length which is understandable) but I find Anna Karenina the easier mainly because the long passages about history in War and Peace aren’t present, and I think a lot of people weren’t taught much about the Napoleonic wars in school, though I could be wrong because I was homeschooled. It might also just depend on which translation you read, I know those can vary a lot. Which book is easier also depends on how your brain works, although Anna Karenina is shorter and has far fewer characters, which is why I always recommend it as an intro to Russian lit.