It’s going to depend a lot on your situation of course. I mean, if you think you’ll use motion sensors a lot and won’t be using the open/close things, then go that route. One nice feature of the motion sensor is that when it’s plugged in it does act as a Zigbee repeater. (In face, in my house right now I’ve got my SmartThings motion sensor rigged up in a window. I’m not using it for motion sensing at all, but rather just as a repeater so my Hub will see when I’m coming home in my cars sooner.)
The AEON motion sensor, in my opinion, is better. It has, in addition to the motion sensing, a thermometer, a light sensor, and a humidity sensor, and it’s about the same price as the SmartThings one.
Now, as for the open/close sensor… the options are many:
1.) Open/Close for door or window. This is the obvious one of course.
2.) Positional sensor for Garage Door. You have the use positional sensor to tell if a garage door is open or close without needing to use the magnet.
3.) Vibration sensor. You can use this to tell when something start to vibrate or stop vibrating. I’ve heard of people who put it in their mail box to tell when the mailman opens the box to put in mail. I’ve heard of people putting it on a 3D printer to know when the printer stops moving and is then a signal that the printing is done. You could do the same thing with a washing machine or dryer.
4.) Switch. I’ve heard of at least one person who uses it at a switch or button. He has it by his bed. You can “open” or “close” the sensor by taking on or off the magnet and have that triggers certain events (turn off the light, turn on a fan, change mode, etc.) Or tab the sensor to make it vibrate and have that trigger a different action.
5.) Temp sensor. I think there is one person who is uses the sensor by some electronic equipment. When the temp goes above a give threshold it kicks on an outlet that is connected to a fan.
There is really a LOT of ways to use the SmartThigns Multisensor. Like the AEON motion sensor, it gives you a lot of flexibility.
So here’s my recommendation: If you’re feel that you will get everything you need in your SmartThings bundle and don’t plan to EVER add additional sensors, then get a motion (or two) and Multis for the rest. But if you think you’ll be adding extra sensors (either SmartThings or 3rd party devices), then I’d highly recommend getting as many Multis are you can. They are just so useful. Then add some of the AEON motion sensors instead of SmartThings motion sensor.