First, about Madrid. Madrid is a really beautiful and nice for living city. You can work hard and enjoy the life at the same time. You dont need that much money to make a decent living (1 - 1.5k€/month). There is a decent community for developers. Moreover, the developers technical level is good or pretty good. Finally, starting a business and managing the business is hard. It is hard because you start paying those 300€ month that sometimes are a big wall. Also, there is a lot of paperwork: taxes every 3 months, hiring someone is the hell, requesting money requires more money in prints than the amount requested.
Chile: The quality of life in Chile is not as good as I expected. The people here is pretty familiar (closed circles) so engaging with new friends is not as easy as in Madrid or SFO. There is a lack of cultural life in the city.
The tech community in Santiago is growing fast but still small compared with Madrid and thousand miles away from SFO. The tech quality is also mid-low.
The management of business on the other hand is very easy. The main problem is when you come here without a link to Startup Chile Program because being a non-tourist here is really complicated. You need a kind of id number - RUT that cant be get until you 5 months after you arrive if everything goes right. You cant have a telephone number, internet or bank account without this number.
SFO is the heaven and the hell at the same time. Lots of interesting people around from everywhere. I was living on hacker community that made my living fun and interesting. The main probloem is the cost of living in the city. And this is a HUGE issue in the midterm for the tech community in SFO. It is too expensive. The community in SFO, no words, just amazing. (I dont say anything about creating/managing business because i have no experience).
Hope this small and partial insights help anyone :)