I've gone from HTC Windows CE > iPhone 3G > iPhone 4 (stolen) > iPhone 4S (replacement) > HTC One M7
iPad 1st Gen > iPad Mini (still own) > Samsung Galaxy Tab S
In my experience transition from Apple > Android and running two at the same time isn't an issue. 95% of the apps I use are available on both devices. There are some I use on Android that aren't on Apple, and some on Apple that aren't on Android. Some Android apps are better implemented (for example RAW developers) and some better on Apple.
The thing is I'm getting upgradeitus on my M7 at the moment however a year and a half on there isn't anything compelling enough out there. Aside from the camera the M7 is still better than the iPhone 6; Higher resolution display, more RAM, better speakers, etc. I've been enjoying (and tiring of) these features for quite some time. Personally I think the M7 looks better than the iPhone 6. That things just FUGLY! You can pick up a used M7 for £150-180 on eBay now! Crazy.
The things the iPhone can do that Android can't I don't really care about. The iPad is going on eBay and I never ask to use the missus's iPhone for anything. The things Android can do that iOS can't I DO CARE ABOUT;
-Downloading from Newsgroups
-Playing downloaded content (in almost any format) without faffing about with iTunes
-Connecting the SD card from my camera to Android and being able to properly catalogue and file the images
-Connecting a high capacity USB key to Android allowing me to backup said images
-Having various background process running backing up specific folders to Dropbox & Google Drive
-Ability to expand the storage by up to 128Gb at a FRACTION of the cost of apple.
--Ability to eject and plug in said storage to my Macbook :).
-Streaming content via Chromecast for minimal hardware outlay.
-Not essential but live wallpapers keep things fresh. I've got the doom guy playing away on my phone background right now :).
Sure Apple devices are OK to look at (except the iPhone 6 and Apple Watch) but they seem to lag a couple of years behind Android & are lacking some key features.
I'll probably stick with the M7 for another couple of years :).