Pros
On some teams you will learn a lot. Thursday free drinks during the summer. In France, BNP is a well recognised franchise and quants over there are quite good. Upper senior management is quite good and understands the market quite well, junior graduates can be very good too.
Cons
Anyone that isn't junior or clearly senior management in trading is subpar, technologies are over 20 years late on most aspects and everything gets implemented inside the trading desks because some IT and Quant keep playing politics rather than working. Middle career managers are completely spineless, incompetent and the few who stay for a long time here are just good at brown nosing. nothing else to get from them. There is a reason why some teams don't have anyone with less than 5 years of experience : some managers are so bad that all their graduates leave in the year they join and more experienced people are stuck there, with no prospect to learn anything or leave. Quant-wise : Most of the technical expertise is located outside of London, in Paris, NY or Hong Kong, London is the political center. WLB : I know of some quant teams where the team members do 7am-1am work everyday and the team manager doesn't understand the projects and focus only on dashboards and PowerPoints to show to upper management, and some other teams that do 9am-6pm with mostly database management. However, the salary is below the competition in London. Interns won't learn anything on most desks because their managers don't speak with them. Only on a few desks will they get to actually learn something. One specific quant team's manager is so under qualified that he redirects all questions to his interns and juniors, what can you expect to learn in that team ? Most teams are made up of seniors with 10+ years of experience and juniors with less than 2 years, the reason there is no one in-between is that as soon as you've understood that the bright people either changed location or left, there isn't much reason for you to stay there. Also, all the harassment complaints made by juniors I know got hushed up and had the investigations begin one or two weeks after the juniors left. I wouldn't recommend to my kids to work here. However, the offices in the other locations ( especially HK) would be fine.