I'm working for a growing company, at a strangely familiar place where it crosses into 100+ people. This is the fourth time I've lived through this process, and the last two had split results (one company failed, the other did not). I was talking with family last night about the crazy amount of business state variety that I've seen first hand, and how so much of it revolves around company size. There are a lot of pros and cons at each stage, and I'm not sure that there's an ideal situation for me beyond feeling that I'm doing good work.
At the bottom is the super-tiny, probably working on contract thing. I did this just once, and it was a miserable failure that lasted about two weeks. This dude bought a small consultancy, and he had a doctor client that had a half-built fat client medical records system. You know, the kind of thing that giant corporations haven't even solved very well. His direction was just to make it work, but there were no requirements and he couldn't understand why it was difficult to make any headway. The lesson there was don't trust people who buy companies that they don't understand. Also be skeptical of anyone that makes you use your own computer.
Then there's the 10+ startup/small business company. These are a mixed bag, and rely heavily on the experience (or inexperience) of the founders and leaders. When you come into them from the outside with a wide breadth of experience, you can impact them quickly. You get to wear many hats, which exercises a lot of muscles since you tend to get your hands into everything. You get the right personalities together, and it's highly collaborative and fun. It's also the easiest level to fall into the trap of over-working, so you have to be aware of that. I've seen this up close twice, and it's fun as long as they can afford to pay you.
Then there's that growing over 100 category. These are exciting, because they almost always have a validated business model and there's a scramble to keep up with the growth and keep it going. There's a maturing process that has to occur, and it's a combination of organic discovery and outside influence. You celebrate the achievements of the past while trying to be self-aware enough to transition to something bigger. It's a puzzle. The first one of these I ever worked in I was very mid-career with a bunch of folks that were more established. It was probably the longest stretch of intense learning I've ever had, for the right and wrong lessons. Not being a primary decision maker, but being near all of the decisions was great. It set me up for everything I've seen since.
I haven't been anywhere in between that stage and a billion-ish-dollar company. Those are different, because they're large and established enough to be what we generally identify as "corporate." They could be big and dumb, or big and agile. I've only been at two, and both were mostly big and dumb. I learned that it had a lot to do with senior leadership, because the attitudes toward innovation and optimization came from the top. I've seen a similar company, from the outside, have the exact opposite because of the difference in CEO. The environment can be stifling or empowering, and again, it just depends on how things roll from the top. At this scale, it's easier for people to kind of "hide" in plain sight, get paid and add little value.
Then there's the super-gigantic megacompany. I've been at three of those. The first was Progressive, and while it was only a contract gig, it was interesting to see how they were future focused, in a strangely "corporate" and deliberate way. They were relying heavily on external experts to coach them how to be better at certain things, and it seemed to pay off at the time. I actually had a few opportunities to go back there, but never did because the commute was insane. Humana was another megacompany, but it was a picture of waste and inefficiency. I could have hid there for a long time, but even being remote I didn't care for it. Then there was Microsoft, my favorite of the huge companies, in part because it was really many companies with the same address. It's impossible for me to generalize about it, because it just depends on where you work in it.
There are two other general categories that aren't really size oriented. The first is government, which is a totally different scene because it isn't profit-driven. The other is a true entrepreneurial effort, where you started something yourself. To this day, the scariest thing about those, to me, is being responsible for the livelihood of other humans. That's a lot of pressure.
I can't say that any of these situations are better or worse, because it just depends on your personality, your career stage, your goals and what makes you happy. It's only important to know where you fit, and if you fit.