As someone who works in web development in the UK (and who's writing an article about this very topic):
1. You're far less well paid than in Silicon Valley. Wages vary by region, but in many European countries, developer wages are closer to standard office worker ones than the rockstar ones at Google and Facebook.
2. Tools are often a bit more basic/old fashioned, and design is usually the same. In fact, I'd say the vast majority of the tech world is usually about 2-3 years behind the valley in terms of tech knowledge and tooling and best practices, and that time gap jumps up further and further the smaller the town/less tech savvy the company.
3. Perks are a mixed bag. Some companies have all the ping pong tables and arcade games and free food/drink associated with startups, some just offer you an office environment and say get to it.
4. Quality of work is usually less interesting. Lots of CRUD apps, small business websites, CMS themes, etc. Very few projects that have the goal of 'changing the world'.
5. The workforce is usually more diverse than in Silicon Valley. For all the comments about women in tech and diversity, my experience is that it's more of a problem with Silicon Valley unicorns than other businesses and agencies. Probably because they're not mostly hiring graduates from a select few universities.
6. The ease of getting a job varies. Usually you don't have much in the way of Google esque logic tests, but you'll probably have a few coding challenges to prove you know what you're doing. These challenges will be extremely easy for someone with FANG experience.
7. There is far less interest in personal projects, side hustles, and other such things among developers outside of Silicon Valley and other major markets. Most devs in these places are basically salarymen, they code because it pays the bills and spend their free time doing other stuff.
8. This lack of interest also seems to extend to the companies themselves when it comes to marketing their tech and culture. In fact, I suspect most European companies are absolutely terrfied of inbound marketing, and have no idea how to update a blog on a regular basis.
9. Working practices are often a bit dated as well. A lot of development is still done with the old 'have the designer create a PSD and get the developer to turn it into a website' mentality, and waterfall style project management methodologies haven't been replaced by agile in many of these organisations either.
So yeah, basically the reality for the average dev outside of Silicon Valley is working on a CRUD project with tech and design that's about 3 years behind the cutting edge with a team that build sites as a profession rather than a 'passion'.