Like any project, a DIY job comes with the risk of improper installation, which can cause polyurea problems in your final product and be potentially dangerous if handling chemicals.
For a concrete coating, hiring a professional is important in ensuring you get the job done right and with quality. A lot of prep work is required for an even coating, and many professionals use a special diamond grinder that you do not find in your typical garage storage.
The diamond grinder sands the concrete down to its smoothest state so that the coating will go on correctly and as evenly as possible.
Deciding whether or not to hire a professional for your concrete coating comes down to your project goals. If you are not concerned with the longevity of your coating, doing it yourself might be the right option.
However, if you want your concrete coating to last, hiring a professional and choosing a quality product will be your best solution.