What are the advantages of switching to an iPhone now that I have a Mac?
Well, apart from better security, the same company being responsible for the smooth operation, Touch ID (aka "actually reliable fingerprint unlocking") and the other advanced features of iOS 8 and OS X Yosemite ... not a whole lot, I guess.
For those who may use Android and Mac, how well integrated do you find your services to be?
Obviously iPhones are going to be better-integrated into Macs than Android devices, this just goes without saying. What's important, however, is whether it all works on the level you use them, as lots of Mac users own Android phones. At the basic level of syncing things, my impression is that this isn't a big issue, based on my Mac-using friends with Android phones. They don't routinely call me up asking about technical issues, which is a sign that it mostly "just works."
Unlike VanSmith, Handoff and Continuity are working 100 percent of the time without issue on my mid-2012 MBP and iPhone 5s after some initial setup issues. About the only thing I'm missing out on is Apple Pay, which I have had a chance to experience personally and am here to tell you is -- very seriously -- the Next Big Thing. For the first time I'm wishing my contract ended sooner than it does (next summer) so I could get an iPhone 6 now, just for this feature.
Of course, as Apple Pay spreads, I think Android NFC-based services like Google Wallet will also benefit, though frankly the former is more secure than the latter. Nevertheless, the point is that the rising Apple Pay tide lifts all NFC boats, as someone from Google actually just said recently.
I think the increasing integration between OS X and iOS -- by Apple's design -- pushes the advantage to the iPhone 6 over an Android device, even putting aside the other advantages the iPhone 6 line by itself brings to the table. That is not to say, however, that there isn't enough functionality that an Android user couldn't be perfectly fine using most of the better Android devices with OS X Yosemite. Clearly, there are many who do.