The consulting title makes it sound like Accenture. They used to use such nomenclature a few years back. If you go for the big 4 just try and check out the culture with someone who is already there. Don't agree with the person who said big 4 types don't make out big time. Most of the niche consultancies have been started by big 4 people.If you go for the start up, you will need to do some due diligence on them: their goals, funding, markets, structure, where you would fit in, will you have some equity, what their USPs are versus potential or existing competition in the market.It depends how much of a risk taker you are and how viable the pitch is of the start up. If you are young enough not to worry too much, you can always get your mainstream career back on track if the start up doesn't work out. You could argue though that your career would be on track if you went for the big 4 option.