The big difference is the level of complexity in what you can do. At the present time, home automation platforms which are available for under $5000 typically fall into one of two categories.
.1. Limited Features, Limited Device Choices
First, there are limited feature systems that can be set up to either run a simple schedule or to respond to a request that you make. You might make this request by Using a voice assistant, like the echo or Google home.
You might make this request by pushing a button which then caused multiple different devices to do something.
You might make this request through very simple sensor detection, such as your phone knowing you had just arrived Home, or the Hue motion sensor you mentioned.
If that’s all you need, there are many ways of accomplishing it. An Amazon echo plus the free IFTTT service plus Logitech Harmony Home Plus some lighting system that works with both Amazon echo and harmony (such as the Phillips hue bridge or the Lutron Caseta SmartBridge), and you’ll be all set.
In addition to time – based schedules, these also typically offer very simple if/then rules like “if I arrive home, turn on the hall light.”
These kinds of setups are what I personally call “limited feature” home automation. Apple’s HomeKit also fits into this category nicely.
2. Full Featured Home Automation
Or you can look at a full-featured home automation platform, which would include SmartThings.
These differ from the first category in two important ways.
.2.A. More Devices to Choose From. First, as you mentioned, there’s a much wider selection of devices that you can use. Some of these may be less expensive, some of them may be very expensive, but there are more of them and they fit more situations. For example, there might be a device that monitors swimming pool equipment. Or the pressure mats that @squidward mentioned. Or just a much wider choice of brand/models for a particular category, like motion sensors.
.2B. More Complex Rules and Schedules But what really causes people to look at full-featured systems is if they want more complex rules to schedule automation.
For example, you might want a rule where if the liquor cabinet is opened when the parents are away but the teenagers are home, a blinking light goes off and the parents get a text notification. Or another rule where if the dog hasn’t been fed twice that day, you get a reminder at 10 PM.
Or another rule where a bathroom light which normally turns off after 10 minutes of inactivity on a particular motion sensor will instead stay on for an extra 15 minutes if the humidity level has been rising in that bathroom (useful for keeping the light on when someone is taking a shower! )
Or a rule to say if the garage door has been open for more than 15 minutes and it’s after 10 PM on a weeknight that isn’t a holiday, turn on the lights in the garage, turn a smart bulb in the bedroom blinking orange and send a text message to the homeowner.
These complex rules usually involve what are called “stacked conditionals.” The limited feature systems can typically do a basic “if A, then B” kind of rule. The full-featured systems can typically do a “if A, then B, but only if C and not if D” kind of rule.
So basically with a full-featured system like SmartThings you can set up much more complex rules and schedules. And work with a wider variety of devices.
Do you need a full-featured home automation platform like SmartThings?
That’s a question only you can answer.
For many people, a basic limited feature system is all they need, particularly if all they want is to put lights on the schedule, use a few sensors, and have a smart thermostat, door lock and a smart garage controller. Plus voice control.
For other people, they want to throw in all kinds of additional complex rules as well as use additional devices.
You should also know that while there are very expensive complex systems, such as control4, that are just as reliable as the basic systems, as of this writing in April 2017, if you are looking at systems that cost less than $5000 then in general the more complex features the system supports, the less reliable it is.
So if you get an inexpensive full featured system you will probably find that you have to do some maintenance on it every week, and you may have a day or so every month where things are not working right.
My own personal requirement is for an MFOP ( maintenance free operating period) for essential automations of at least six months and preferably a year. I’ve gotten that from Amazon echo, Logitech Harmony home, the Phillips hue bridge, Lutron Caseta light switches, and apple’s homekit.
But since November 2015, I have yet to go 10 days without SmartThings requiring some kind of hands on maintenance. I still like it for those really complex rules, and for some specific devices, but now I only use it for convenience notifications like letting me know if the guestroom window was left open when rain is expected and the guest is not home. I can’t do that kind of rule with a simple system.
But when it comes to having the porch light turn on at sunset every day, I no longer use SmartThings for that.
SmartThings will offer you more devices to choose from and the ability to set up much more complex rules. But it’s not yet as reliable as a simpler system. So each person has to choose for themselves whether the greater power and versatility of a system like SmartThings is worth the additional maintenance requirements.