Vantaggi
There is good initial salary. Compensation improvements are widely dependant on internal politics (if you are not chinese). Not much more to say. Looks like a good starting point, not a point to further develop your career.
Svantaggi
Nowadays, Huawei is outsourcing most of its departments in Spain (and Europe). This means that the new "employees" don't count as "headcount" - this truly limits the involvement of employees, and the access to several internal benefits (such as health insurance) There is an actual weird policy of classifying employees based on their ethnicity (its not official) there is a big difference whether you've some kind of relation with China, or not. Many conversations and meetings will be hold on Chinese - or there will be timeouts off the meetings to handle details and approvals on Chinese. This is not a company to escalate or develop your career: the threshold you can escalate is quite clear, since middle to high management positions are reserved by policy to chinese (and they change every now and then with expat rotation) - the expat rotation creates an additional risk: every new expat that comes, usually wants to come with his or her team, causing problems with the locals.