What do YOU want to do? Forget what other people are telling you to do, after all it is your career (and life!), not their's. It sounds like you are really happy at the small firm, they value you, give you opportunities and want you to stay around. At Deloitte, you will just be another consultant. Think of it this way, would you rather be the big fish in a small pond or a small fish in a massive pond? The grass is not always greener, you've got it pretty good!