Differentiating via OS doesn't work, that's not opinion
Tell that to Apple...
This simply tells me you haven't even seen either Blackberry's latest OS or Android since version 4.
My first BB was a 7290, my current phone is a Z10. (While I'm a long-time user, I'm no die-hard, I'll happily give up my BB if something better comes along.) My wife and a few of my friends are Android fans and I've done some Android development. I'd like to think that I have a reasonable, if admittedly limited, familiarity with Android.
Blackberry have even gone as far to copy common icons such as the 3 dots for menus and so forth. Many other UI elements are exact copies of Android.
You're not very familiar with BlackBerry are you? From their gesture suite to their approach to multitasking, BB10 is about as close to Android as Android is to Windows 3.1. Given your list of similarities, you might as well claim that my car is just like a bicycle because the wheels on both are round. Or, for a better analogy, that Ubuntu Linux, Windows, and MacOS are all identical because the close icon is a little 'X' along with a host of other similar icons 'copied' from Windows 95.
They're rather dramatically different. I honestly don't see how you can claim that they're similar at all.
Sure it's very different under the hood but that's not what I'm talking about here because that's not what users see, I'm talking about the fact the UI is a poor clone of vanilla Android 4 with a few ideas stolen from iOS too.
You couldn't possibly be more wrong. If they stole from anyone, it would be Palm. I've see many, and even made my own, comparisons to WebOS as far back as PlayBook OS. You'd be the first I've seen suggest that BB10 is anything like Android. Probably because BB10 is absolutely nothing like Android.
Have you even used PBOS or BB10?
The problem is that Elop wasn't the person to do it and a focus on WP8 wasn't the way to go. Both these things were done to make Nokia an easy cheap takeover for Microsoft
Wait, so you're saying that Nokia purposefully tanked itself by hiring Elop and switching to WP8 so that Microsoft could cheaply and easily take them over? That doesn't make any sense.
Android was the easiest path for it to stay a strong independent company, just like Samsung.
See my earlier post. The only company that benefited from Android was Samsung, and there's absolutely no reason to believe that it was the OS that made them successful.
Android isn't that great, and it's one of the worst mobile platforms for developers -- even BlackBerry has them beat there. (I know the meme, but a lot has changed over the past few years.)
Android is on top because it's inexpensive and open. As I said before, they will fall very quickly the instant an equally inexpensive and open platform shows up that has a better UI and/or is easier to developers.
If differentiating via OS is the key as people like you seem to think it is then why are Blackberry, Nokia, and the Firefox phones all failing?
BlackBerry is having trouble because of the 'they're dying' meme, which is only true now because everyone believed it when it wasn't true. The hardware is solid, as is the OS and UI. Those all got high-praise from even their worse detractors (like BGR). Their weak app market and the unfounded belief that they could go under at any moment were their biggest problems.
Nokia was, and still is, horribly mismanaged. Do you actually think switching to Android would have magically saved them? It sure hasn't helped Samsung's competitors!
The Firefox phone didn't fail because of the OS, it failed because it was pitifully outdated at "launch" and sold (exclusively?) through eBay. Then again, it may be too early to say that it failed. It's difficult to say that it's even hit the market! It's more like a 'sneak peak'. It also doesn't help that it got more than it's fair share of doom-and-gloom press months ahead of their "launch". I don't know enough about it to meaningfully compare it to Android (either on technical or UI grounds). I'd leave that up to you, but ... well, see above.