One note if you have surface pro, notability if you have iPad. You can do visa-versa and it still works fine, but I've found that using the note-taking app that was originally designed for your device can be a little more intuitive. I honestly haven't tried it on Android tablets. And there is seriously a plethora of note-taking apps out there, but I've looked at several and I still think the mainstream/most popular ones are probably the best ones.