[carise]

As mentioned here, it depends what your motivations and career aspirations are. Working at startups (worked at one mature startup, then consulted for a bunch of small ones) gave me experience dealing with customers directly and delivering high impact in a short timeframe. Working in a big company is teaching me to think really big (reach big customers, scalability/performance, high ROI, etc) and giving me the opportunity to learn from many, many brilliant people.