It comes down to the fact that you can run malicious code a lot easier on Android comparatively speaking. Sideloading APKs allows for greater flexibility in terms of installing applications that cannot be found/are removed/rejected by the Play Store yes, but with respect to users that sideload APKs and AppData (pirates, not you specifically @MksTn) it opens the door to easily phish for their information. Considering the fact that a lot of Android users are stock users either by choice or imposed, it makes it that much easier for malicious injections to go by unchecked since only a handful of ROMs have appropriate checks baked into them, or, you can install certain "tweaks" or applications via Xposed to do it, which again requires root and/or an unlocked bootloader.
Apple's choice in maintaining a closed door policy makes them extremely attractive in terms of information security (which made Blackberry a go-to in the past), particularly in an age where business are willing to wage data warfare, corporate espionage cripples competition in the business, so that's a pro for it. Playing devil's advocate, I do agree with you though, you paid for the phone, so you should have the option of essentially doing whatever you want, but since you're using proprietary software owned by Apple, they do force you into a position of either picking/using them with restriction, or not at all, with jailbreaking being the solution of sorts depending on how you use it.
@johnmcc07 that's the bane of Android honestly. Updates aren't pushed out regularly or as speedily as many users would like, particularly when they're not using a GPE/factory device (i.e. carrier variants). Being on the Verizon M8 as my person device, I'm better off going for something like Cyanogenmod or some AOSP/Nightly ROM to get actual updates than to wait for Verizon who usually pushes the update out about 6-8 months after the GPE release, and even then it's still buggy.
