I took a look at all four of the suggested apps -- two for simple presentations, and two for whiteboards. There were pros and cons for each, though to be honest, some of the cons for the presentations are deliberate choices by the creators.
I do like to have the ability to create very simple presentations on the fly -- both Deck Slideshow and Haiku Deck, by limiting what you can do, force the concept of "simple" -- which can be a good thing for those of us who have a tendency to over do PowerPoint presentations. What I liked about Deck are the different themes that are freely available -- they are fun and add a little "kick" to the presentation without having to figure out how to do transitions. I also like that there is a set of readily available formats that can be customized, to a certain extend -- these include bullet pointed text, charts & graphs, tables, inforgraphic style diagrams and the ability to insert images. You are limited to one font type, but having to choose between too many font types can slow down putting together a presentation. I am not as fond of Haiku Deck. It took longer to figure out how to create the presentation, and I do find it interesting that you cannot re-arrange your slides once you have created them -- I had to copy and paste the slide I wanted to move and then delete from its original position. It also has a few less functions than Deck, such as tables and diagrams.
As for the whiteboards -- I really liked Lensoo Create. It was pretty easy to use and figure out how to use the various functions. I found Educreation more limited. Lensoo, beside being able to just write on the whiteboard, type or add images, also had a suite of figures (squares, triangles, graphics) and a few font options. Educreation was limited to whiteboard writing, typing (fixed font) and image insertion -- with Lensoo, images were easier to manipulate, with touch screen moving around, enlarging, shrinking and rotating, which are a bit more cumbersome in Educreation.
I did find it annoying that you had to add voice recording before being allowed to save your whiteboard creation -- and in Educreation, after saving the "lesson", when you bring it up again, it automatically plays, with then an annoying pop-up that asks if you want to repeat (you have to then click "done" to get rid of it.). Lensoo, on the other hand, waits for you to start the "lesson."
I can see where the whiteboard apps can come in handy when you are in a meeting or conference and you want to either record what is happening, or decisions being made -- just like any whiteboard in any conference room.