Ask HN: To Join a Startup or to Join Company?

I am currently contracted as a part-time developer and the contract ends this month. Friend of mine asks me to join his IoT startup* (aka. become his co-founder). He is very passionate and very energetic when he is talking about the startup. The problem is i don't see his point this startup would be succeed (even though 10 years ago he started a startup and succeed). He has said about the strategy: to make awareness about this new technology, first we would do consulting. Once we have enough idea, we will make a product. I don't like his consulting strategy (because most clients sucks), but yes we don't have any idea what product to make.

At the same time, i am offered a job in a company, with high enough salary (at least, high enough in my area) and good environment (At least they understand Joel Test). Also, they have single working product, which i will be working on, if i accept the offer.

What should i consider to make decision (to make startup or to join company)?

* in addition: i don't live in the developed country like US. Here, internet of things is still new (yet it would boom eventually). Just like mobile app market, it took 2-3 years to bring smartphones become popular here.