Rated in descending order, these studfinders represent the basic technologies available today: conventional electronic studfinders; UWB or radar finders; old-fashioned magnetic rod finders; rare earth magnets; and good old human intuition, a type of studfinder by itself.
The problem is that anything--any bump in the wall--will make the rod flutter, so it's impossible to discern if you've hit paydirt or not. Back in the old days, these studfinders had their place in toolboxes. Today, with more advanced and fairly inexpensive dielectric studfinders available, there is no need to purchase one. These rate among the worst tools I have ever used.
Slide the studfinder across the wall. When you near the edge of a stud, a light or sound will alert you. Make a mark. Carry the device to the other side of the stud. Move toward your mark. Pencil in the other side of the stud. Hopefully, the two marks will be 1.5" apart--the width of a stud.
Electronic studfinders get high marks because of their low cost and relatively good accuracy. What I don't like are the antics involved with finding the right and left side of the stud. However, one sensor which we haven't reviewed, the ProSensor, appears to take into account the full width of the stud.
So UWB scanners are clearly more than just studfinders. As a casual DIYer, you may not have an interest in UWB scanners' many delights. You'll also want to note that these do not come cheaply. They are priced more for the professional trades. The Bosch D-Tect Wallscanner costs over $800.
A colorful, simple, nifty little device that finds studs without fuss. The black cylinder has an inner knob that looks like a colorful game piece from a board game. When you sweep the wall and hit a fastener, the knob springs upright. There's not much else to say, other than that it works.
I'd rate this #1, except that the price ($9.95) makes it difficult to justify buying a handful of Studpops. It's nice--though not necessary--to populate a stud with a line of those round yellow magnets in the Magic Stud Finder kit. It's a great way to visualize the stud. Or you can put some on one stud and a few on the adjoining stud, in order to see the relation between the two. The cost of Studpop would make it prohibitive to purchase four or six of them to do this.
What really makes this a studfinder-on-steroids is the rare earth magnet. The brand I use is called Magic Studfinder. Rare earth magnets, if large enough, can mash fingers beyond recognition (don't worry, these magnets aren't that powerful). But they are powerful enough that they will practically leap to a fastener when they get within a couple of inches of it.
The downside of this or any other type of studfinder that senses fasteners is that fasteners are often not located on the center of the stud. For example, if you are dealing with drywall installed parallel to the studs, the fasteners alternate left/right of the on-center line. Thus, don't just locate one fastener and assume that this is the stud's on-center point. It's best to lay down four or more (the more, the better) magnets to get an average representation of where the center line lays.