You make moodle seem rather basic and monotonous. May I suggest you first of all try out moodle, as it is free to use. When you have tried it out , created a few quizes etc let us know what you think. Yes Moodle can be an online quiz, but it's much more as it is a learning management system (LMS)
When I checked up on this quizdom system's website I couldn't find out very much about it, and not enough to convince me if it was good enough to meet my needs, and what turned me off was no price tag? Simply a request ASK FOR a QUOTE. That put me off immediately.
I don't think Quizdom is an LMS. In fact it is probably only comparable to not much more than two of Moodle's plugins.