I'd like to ask you guys for a suggestion: I've been working for about 10 months at a friend's little startup as a front-end developer.

There are only a couple of developers in the team, while the CTO and some other senior devs are either absent or passing by sporadically, as they actually are not part of the team, with all the problems that this entailed, so for various reasons I didn't much enjoy the company in terms of organization, culture and growing opportunities, to say the least.

A couple of weeks ago a rather renowned company interviewed me, and told me they like my attitude and could consider to take me onboard in a few months as a fullstack developer, provided that in the meantime I level up my backend skills.

Now, I'm struggled as on the one hand I would leave my friend's company, but on the other hand, the latter company's working culture seems great, and I expect the compensation to be higher as well.

What would you do if you were in my situation?
Thanks for any suggestion :)