Bachelor's level degree was mainly technical, that is, preparing you to handle engineering problems, but pursuing the Master's will expose you to economics/business, too. A large part of the engineer's job, regardless of specific discipline, involves making sound business decisions. Going for the Master's in engineering gives you exposure to the basics of business and it is a natural extension to then go for the MBA. Get your engineering out of the way first.

You need to decide what your end game is and look for jobs in that field and see what they require. My guess is that if you really want to be a true engineer and expert witness etc the masters in engineering would be best. If you want to start your own company someday perhaps the MBA. But find out what those hiring for the job you want are requiring before you decide.

Engineering. The world doesn't need more business people.