Not sure if trolling but it's been said at many events from Apple directly that they're making an OS that works best for the device. OSX works best for a PC and iOS works best for mobile devices.
You obviously disagree and therefore you have a choice to go with the platform that suits your preferences. Being a computer science major in college working with nothing but windows I can safely say my preference is OSX based on both professional experience and personal experience working and troubleshooting both platforms.
As far as side by side multitasking, yes it'll be great if we get it for iOS however I've rarely found the need for it when using automation apps like Editorial, Drafts, Pythonista, Launch Center Pro, and Workflow.
Windows has always went in a different direction then iOS despite borrowing elements from other companies (see reviews of Vista and win 7 and how they directly mimicked OSX) but I for one was glad when they announced one OS to rule them all. It limits them and to escape the said limits compromises will be made. There's already been numerous issues making an all in one platform as well. Windows 8 & 8.1 was rushed, wasn't throughly thought out and Ball re even stepped down due to that and poor sales.
Regardless if windows (9) 10 is good or not most people I personally know of got tired of beta testing windows. Happened with Windows 2000, Windows ME, Windows Vista, and Windows 8. Windows XP and Windows 7 were the only good things they've made besides office and even if Windows 10 is the perfect OS many of us are tired of their approach, the way the OS is laid out, and lack of many things OSX & iOS includes for free.
Go with what works best for you and what you're willing to deal with as nothing is or ever has been perfect and without issue. The fact apple makes an OS specific for certain devices and Windows isn't doesn't make one better than the other and in fact there are many issues with a one size fits all for Deas as well especially when there's as many OEM's and devices as windows has.