about me: I'm 24 years old and recently switched companies.
Company A: I do now work for a medical mid-sized company, with a old IT and old structures in a boring job but I do get paid good. 3343 monthly for 37,5 hours a week, with 31 days paid vacation. Working here does not benefit my knowledge that much. (I have the option, to learn while I work, as I have some spare-time between tasks.)
Company B: I got an offer from another start-up like company, with a very interesting job, doing what I like. They pay: 3000 monthly for 40 hours a week, with 30 days paid vacation. Working here, would benefit my knowledge for my future plan greatly. I would not have that much spare-time between tasks.
Future plan: I am in the progress to start my own SaaS, this is why the question is tough to me. I am able to write code and host servers, I do not need to learn much, to start the SaaS but still, I do not know, if I should take the offer or not. I really tend to do so, because I think it is better for my future. -------
Can you give me advice in my choosing?
I would note that 40 hour weeks, in my experience, are very rare in technical roles if you're at a "start-up like company". Be prepared for 60ish hour weeks (and celebrate if that doesn't happen).
I'd definitely recommend working for a startup at that age and (almost) no matter the startup it will really level up both your software dev and business knowledge but I think the salary is a sticking point on option B as it stands. (though I'm not sure what your pay is like relative to the market in your location but generally I've found startups able to make better offers than large companies)
You're early enough in your career that it's probably not worth moving backwards in salary at this stage. Find a startup who offer an increase or at least a match while coasting in your current role.
Source: I been in the same position as you were (I'm 27), and I do not regret any single time my choices. Even today, I decline any positions at companies such as company A.
I see it all perfectly; there are two possible situations — one can either do this or that. My honest opinion and my friendly advice is this: do it or do not do it — you will regret both. (Soren Kierkegaard, Either/Or: A Fragment of Life)
Your question is about personal choice - do not rely on strangers in the internet.
Personally, I would go with B, even in 34, fun and growing are my top priorities, and money difference is too small to care about (for me).
40 hours/week sounds unlikely, a and it can actually get pretty hectic if those hours don't include commuting.
There's also a lot of work in a startup that's just putting out fires or dealing with badly designed code, so you might possibly not learn as much as you expect.
Personally, I'd prefer company B but it might be a roadblock for your SaaS plan.
Assuming Company B is the better fit, ASK them to match your current compensation package. That will keep you at parity.