Monoprice devices are inexpensive for a reason. Simple and cheap, so just depends on what you’re looking for.
I think right now if you live in the US at the Lowe’s iris motion sensors are probably the most popular. If you get a 10% off coupon from Lowes, which they seem to distribute pretty regularly in their sales flyers , you can get a very good price. You’ll find lots of discussion in the forms about them. The following thread discusses the various features that motion sensors might have and why some cost more than others. But the truth is they’re all pretty good. The more expensive motion sensors have more features, but you may not need those.
All of these PIR motion sensors work on the same principle, which is measuring a change in heat as it moves across the Detection field. For this reason you will get the quickest and most reliable detection if you don’t place the sensor so that the person is walking straight towards it. Instead you want to catch them moving across the field. For this reason some people place them on the ceiling pointing down others place them on the wall crosswise to where the people will walk. There are some sensors specifically designed for ceiling mounts which have a wider angle to catch people coming from both directions.
If you have pets, you’ll need to think about whether you care if the pets’ movement triggers the motion sensor or not.