What are the benefits of Apple products?
If you have an iPad, an iPhone and a MacBook Air, the major benefit apart from the fact that one can access data across devices is that you can show your friends how wealthy you are ;)
Not that you can't get similar integration across different platforms, but some of it is unique to just Apple. For example,If you use Fantastical on Mac, but not on iPhone or iPad. It still syncs everything automatically through iCal to your phone and iPad. Your music, notes, emails, safari bookmarks, contacts, reminders, and photos are all automatically synced. Take picture with your iPhone it's automatically in photos. Make a note in the notes app on your iPad, it will be already on all your other devices.
Having an iPhone and more Apple products is where you get a huge bump in integration, as you get iMessage/FaceTime everywhere (along with photos). Having a MB and an iPad will let you sync all the iCloud stuff (contacts/calendar/reminders/Safari/notes), and there are a lot of really good apps that have excellent iOS/OSX support. iTunes also runs best on OS X, and it really really is a terrific music manager and Photos is awesome if you're not really going to edit them much and just need them cataloged.
There's the resale value to keep in mind .old MacBooks are still able to be sold to recover a reasonable fraction of the purchase price. And the no-hassle in-store warranty, for that make sure you get AppleCare on all your portable Apple products. If you ever do have a problem.
Easy to pick
The product lines are clearly delineated and there's no huge range of devices with very small differences you have to parse between to make a decision. You can trust Apple with your digital life because they have a clear vision and the structure (and cash) to work towards it.
Because its cool
The Mac mini and MacBook can be used together via "Screen Sharing" and that's the coolest thing ever. You can control the mac mini that's connected to my TV via your MacBook. This is great because the batteries always die in the keyboard and mouse.