I have no doubt that Romney or Newt would be OK. Newt is a dynamic speaker though and is likely to be able to shape the agenda much to his liking. He pushed things through congress before.
So I’d actually be MORE concerned with Newt getting bad policies through the process than I would be about Romney, who seems much more likely to sign what comes to his desk.
Gingrich is more conservative than Romney, but if the choice is which one to elect given a majority in congress, I’m not sure Gingrich is the “better” choice. Unless you like his plans for things like immigration and government health care and striking the good middle road on global warming.
I can’t imagine any global warming or amnesty bill getting through the House, which is and will be more conservative than the Senate. I think it will be easier to get rid of Obamacare with Newt.