This has been much discussed in the forms, so if you just search on any one of the hubs you’re interested and you’ll probably find discussion.
There’s no one right answer right now. It just comes down to the specific features that are the most important to you. I will say that video is not smartthing’s strongest suit. But then echo doesn’t tie into video at all, so it just comes down to what you personally need. SmartThings is also fairly weak in audio/visual because there’s no IR Integration other than through harmony. But the harmony integration will be enough for a lot of people. (It is for me, but I mostly just switch between cable and roku.)
My own belief, as I’ve stated many times, is that by the summer of 2016 there will be at least three and probably more like five or six reliable, mostly plug-and-play home automation systems under $5000 that have some voice and some video. HomeKit/Insteon will definitely be one. Echo will be in there somewhere if only as an add on to other systems. I fully expect SmartThings/Samsung to be another candidate, but nobody is there right now in this price range.
If you can spend $3000-$10,000 per room, you could have it all right now with one of the high-end systems from control4 or Crestron. But most people looking at SmartThings are thinking more spending in the range of $200-$500 per room. And not every room.
So you’ll get lots of opinions, but no one answer. 
For the separate issue of a security system, start here: