What are the most striking differences between startups and established companies?

There's more stability, structure and work-life balance at more established companies.

Organization. Whether you like it or not, you will be wearing multiple hats in a startup and feel less valued because everyone is on damage control mode making sure they don't run out of funds

I really haven't in Counter- striking difficulty

Few safeguards in startups versus documented processes in established companies.

Established have loyal customers

Speed of decision making, risk tolerance, amount of process... short term vs long term orientation.

A startup is searching for product market fit, which means it's testing various hypothesis and attempting to answer a question: "how do we get paid to do this (or that) thing". The amount of time it can try to answer this question is limited = more risk, possible more reward (often at a total loss) A company has already answered those questions and only asks "how can we get more (or existing) people to pay us for this" & "how do we optimize the value of this..." so you iterate on making parts cheaper/more efficient, finding new related things to sell to existing customers, or possibly attempting to sell something new to someone new... the amount of time it can try to refine this problem is greater = less risk, possibly less reward (never a total loss)