Advice regarding a new Nest Gen 3 to replace Gen 2 keeping WWN or moving to Ecobee 3 lite

Have a new AC unit on order which may benefit in having me move from Nest Gen 2 to a newer thermostat - Nest Gen 3 with optional temperature sensors for a couple of bedrooms or to an Ecobee 3 lite with their more expensive occupancy/temperature sensors. I have a few concerns:

  1. Reliability of the cloud server - Nest has been good overall, but I’ve read a few complaints on Ecobee
  2. Ability to add the new Gen 3 into my current Vera & Alexa ecosystem [WWN] w/o breaking what exists now; in other words, may I simply add the new Nest Gen 3 thermostat to my current Nest phone app and Vera Plus [deleting the Gen 2] or will it force me into a Nest->Google migration - at which point I will likely have to return it?
  3. Ecobee integration - is this any better with Vera; the app seems dated and what of their cloud issues
    Your input would be most welcome. Having gone over this again and again, I’m at an impasse and wondering if I should make any change at all. Centerpoint provided a $50 rebate good thru end of year and HD has a good deal on Nest Gen3 bundle with 2 sensors for now - bringing price to ~$200 or about the same as the Ecobee 3 lite w/2 sensors. Wife likes Alexa integration with our Nest Gen 2, but who knows how long that will last. Frankly, I just don’t have any real knowledge/track record with Ecobee, but they seem to be well-liked in many reviews. Ultimately, Google will do whatever is in their best interest. Thank you!