I've been a landscaper for years and do jobs exactly like this regularly. I'd say do some research on individual local landscaping companies. I have to think there are plenty of companies in your area that would do this job to your satisfaction and for a fair price. The blade trimmer can get the job done, sure...but they are not really quick. Personally, I'd probably try and see if I could run a Bobcat in there and clear the area really quick with that. Having a crew come in to do it also means they get to pick all the thorny stuff up to take away.
Also note, a company that is strictly brush clearing tends to be a bit more 'rough around the edges' so to speak than a landscaping company will be. Different focus. It really depends on what you want that area to be once it's cleared.
