It's true that EAD application

is seldom rejected and it doesn't come with employer and working hour/field restrictions. However, using EAD before your 485 approval doesn't mean that you could work on whatever you want. Before your 485 approval, it is always possible that USCIS checks (usually through interview) to see whether you are working in the field of your expertise or just in MacDonald.

Also, H1B is safe in case your 485 is denied. While EAD becomes invalid immediately after 485 denial, together with your legal status.

So you have to use EAD and H1 wisely to get the most out of them.