I had a rooted Samsung Galaxy and now a Lumia 520. There is no customization option, no File Manager, unable to attach a file directly from mailbox (have to share the file directly), never stay online in chat apps unlike Android, no basic apps in market like a proper sync calendar, a good ToDO apk (like AnyDo for Android), and a lot more problems here.
I wish Microsoft make this an open source just like Android. If I could somehow root my 520, I think this phone can rock than any Android coz apps are really light in here and there is no lagging like that of Android. Finally, I would suggest 520 only if you are looking for a change. Never compare this with Android.