I'm similar to you, primarily a BlackBerry user (Z10 being the latest), though I've dabbled with iOS and Android in the past on secondary devices. Been curious about how I would like Android as a daily driver smartphone, so I decided recently to give it a shot. My shortlist of devices was similar to yours, with exception of the Note 3. A phone of that size just does not interest me. I ended up getting a Nexus 5 over the others for a few reasons:
Value for dollar/price - I'm buying this phone off contract, so to be able to get what is considered top end hardware for the price of a mid-range device was very appealing to me.
OS - Having a Nexus device will guarantee you get OS updates for a certain amount of time. No waiting around for a manufacturer to get around to it, or not do anything at all. Also, it's stock Android, which I'm familiar with from owning a Nexus 7. No bloat or OEM interface layers, just Android as Google intended.
LED light - Yes I know this sounds silly. But you're a BlackBerry user too, so you know why this is important to me
Which BlackBerry device are you using right now? I can probably give you some thoughts as to how the Nexus 5 compares to it...