It is hard to say which one based on information you’ve provided, but if I were to pick one then it would be electronic trading. There is a lot of work around etrading happening due to regulations and it is one area that will remain very important for the foreseeable future.

Anyway, it really does depend on what exactly those roles entail and which organisation you’ll be working for. If electronic trading role gives you an opportunity to develop low latency stuff incl connectivity, order routing, order management, algo execution/strategies, etc; go for it. If risk system involves quant development, real-time pricing stuff, GPU coding, etc; then it depends on what interests you intellectually. Do note that most of the available work around risk systems is simply picking stuff up, aggregating/processing, and putting it somewhere else. Users are mostly MO/Risk teams.