I have read that the corners of the wobble dado are rounded instead of square.
The bottom of the cut is slightly rounded. That
usually isn't really a big issue no matter what you are doing. The cut is generally a little bit rougher than one from a stacked dado set - if you are building woodenware for bee keeping it isn't rough enough to be a problem.
A wobble dado will do the job cost effectively for most occasional wood workers. If you are building high end furniture or just want that warm feeling that you get from using a fine quality (expensive) tool then you should go for the best you can afford. Of if it's going to get lots of use.
They are both potentially dangerous, but a table saw is anyway. Any dado blade can really kick back if it's misused. I mentioned that it's a lot better if you can have a dedicated saw for your dado - that is partly because you can keep it set up with a feather board which makes it a lot safer. In my cabinet shop days all of our work was designed to use a dado that was 1/2" wide and 1/4" deep and the saw was locked down to that setup. Then we used auxillary fences (made out of hardwood) to space the cut from the edge of the piece. This arrangement made it very safe, accurate, and repeatable. Otherwise, every time you change setups you have to mess with it and run test cuts - burning lots of time and wasting material.