As a civil engineer with 10 years experience, I think you are looking at this the wrong way. Assuming that these are consulting firms that you are comparing, the only things that should matter are the projects and the firms' reputations in your local market.

In your position it is irrelevant if you like your boss or your current salary. If your boss can bring in good projects and gives you good exposure to the various aspects of how they are delivered, then you are in a good position. If this other company has a better reputation, better project backlog, or will give you more autonomy, then by all means go there.

I wouldn't consider company size to mean much. All companies pay the same because the competitive bid environment means your salary will always be tied to the charge out rate in your local market. Also this idea that larger companies will pigeon hole you is not always true from what I've seen. Lastly, even the biggest companies have bad market penetration in some geographies, and that needs to be carefully considered before taking a new job. I've seen people regret taking jobs with companies with great reputations globally cause they had very little market presence locally.

I would also say that reddit is not the place for civil engineering advice. Talk to colleagues that you trust and will respect your confidentiality. Civil engineering is an old profession with its own eccentricities that are unique and don't necessary have analogues to other careers. To be successful in this career you need to always be playing the long game, and not focus on short term issues like current salary or personality of coworkers.