Let's compare the lead up to BB10 to WP8's lead up; where MS failed to provide developers the sdk in a timely manner. The unfinished BB10 prototypes work better than the finished WP8 phones. The BB10 OS itself is far more fluid and has better features than WP8, who banked on the currently bad implementation of Live Tiles as a selling feature that aren't so live after all. No notification center, for which the lame excuse is "we ran out of time". Wha!? Random reboots, a grocery list of other bugs and glitches that even the BB10 alpha test devices don't have. A 400+ post thread stickied in the WP8 forum for a place to criticize problems. OTA updates at the mercy of OEM's and carriers is Android fragmentation all over again. I have to stop here because I can't even begin to list all of the grievances against the WP8 phones here because the count so far is too large an undertaking. Using MS Office on the phone is certainly a good feature, but for every good feature I've seen people point out in order to state why WP8 will succeed I can only reply: If that's the case, why aren't the sales numbers reflecting that?
BB10 is going to deliver a far more solid user experience, and when the Q4 2013 results are in for both phones, I'm going to be able to prove it. It would take a combined effort of Samsung, HTC, and Nokia to hope to outsell Blackberry 10 devices, and even then it's going to look a lot more grim for Nokia, who's whole future is riding on WP8, and people are going to (and already are) looking to Samsung's and HTC's Android offerings before the WP8 devices. How many people are looking at the immensely popular Samsung Galaxy S3 or Note 2 vs. the Samsung Ativ and saying "I'm going to go with that Ativ!".
Even IF the BB10 were to flop, my choice would be the same as what you're already seeing everyone else do: Buy an iPhone 5 or an Android.