If you are real and indeed got a quote that was cheaper than AllPcb, you may just try them and see what happens. It is possible that nobody uses them because they did not make nay effort to advertise.
It is hard to tell without knowing your volumes, complexity of the board, etc.
I have not tried, but I heard that AllPcb works fine for moderately complex boards. But so are many others. In this market you are likely to have a good experience rather than a bad one with any known company.