Soon, Realm will be available for Android too. I was told that you could use the same .realm databases across multiple platforms. Just imagine what you could develop with that huge advantage of sharing the same data models over iOS & Android. That's something you could very hardly achieve using CoreData/SQLite. Besides that, Realm is in continuous development, so we might see some more platforms support in the future.
5. Free, Well-documented, Other Features
Some of you might not be surprised that Realm is free, but just take a look at all the advantages you have compared to other similar solutions and you'll see that this is a pretty awesome. The guys at Realm worked really hard on their documentation and what i especially like is that is very straight forward. If you have a question on a related feature, you will easily find your answer. One more thing some developers might like is that Realm supports Objective-C as well as Swift, which suggests that this would be a long-term solution for iOS Developers.
I didn't went in much technical details about it, but Realm means way more than you've just read. Right now it's in very early stages but with the help of an amazing community, i am sure it will grow a lot. It supports relationships, migrations, background operations, notifications, etc. I highly recommend you to check it out on Realm.io and give it a chance for your next project. I promise you won't be disappointed.