Design/R&D is great place to start at a company. If you discover that it is not your cup of tea, It's much easier to go other directions from Design department(FAE, technical sales, production, project management), than the other way around. Be prepared that you might need to see few different jobs/companies to discover what suits you. One observation in regards with a regular job(not 3 month internship) - If the place drives you nuts, or feels bad, or in general/on whole does not suit you in first few weeks, leave. That's what is the probation period for, to see if works out for you or not. The place won't change. Don't waste your time and energy, there is limited supply.
Did you interviewed(again, the job interview goes both ways) both potential bosses? Which one was better?
What are you passionate about? What is your dream job? Which of the two offers brings you closer to it? What are the other options that you are not thinking about?BTW other companies might be willing to pay for your masters degree as well, once they know you.
Although the pension is far away for you, own living and family might be a bit closer. Check what are the subsidies and benefits for young people, or construction savings and some similar stuff. Sooner you start, better off you are. Every $ counts. Spend few nights reading about it, your future you will be grateful.
Job security is you, not the job. 2 years in a high tech and fast paced company might do for your career much more than 5 years in another place.
If you are great at what you, you will be fine
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