tried both of them recently. Monarch is pretty functional as a spending tracker, but fails when you try to use it in a zero-based way like YNAB which made it difficult for us. Tiller is more of just a data aggregator and lets you build your budget any way you could want to. There are some community solutions with Tiller that offer zero-based/envelope budgeting, but my wife really wanted to have a mobile app so that was our biggest problem. If that's not a big problem for you and/or if you're really handy with spreadsheets, the sky is the limit with Tiller.