Both of these online resources can be used without creating an account. However, if you do decide to create an account more options will be available to you.
In each case, when you create a wall, the wall has an associated URL you can pass along to others to collaborate and add their stickies.
Both of these tools are iPad compatible, so end users can be on a computer or mobile device.
Padlet allows you to change wallpaper, which can include any photo you wish to upload or point to via a URL. For instance, you can have a map, and ask students place stickies on certain locations.
The wall is identified with a random URL, and Padlet does allow you to create your own unique URL. This will allow you to create easy to remember URL's for students.
You can have stickies freeform or streamed next to each other. There are no formatting options for the sticky notes, however you can upload an image, video, or add a link to your sticky (note: uploading not compatible with iDevices)
Primary Wall provides you with a default background, and you are unable to change this background without an account. This is a great word wall to use with younger students because of the limited options.
When selecting a sticky, you can choose from four different colors, but the font and size is set for you. You can not upload any other items to associate with your sticky.
The feature that Primary Wall offers is the ability to Sort or Search throughout stickies. If you have 30 stickies, when you Sort them everyone's wall will view them in sorted order. You can also Search for a sticky containing a particular word or phrase found anywhere on the sticky.