Currenly I train in 3 aspects of the martial arts: kuk sool won ('traditional' martial art), mixed martial arts and krav maga.
Although I enjoy aspects of all 3, I find the MMA and krav to be relentlessly practical. Possibly they're more effective as well, but I'm fairly new to kuk sool so will not judge it based on a beginner's knowledge.
For me, it is good to train on 'both sides of the coin', as it were. I think that if you want to be a well-rounded martial artist you need both the traditional and modern styles. It is also very good for the general humility to put on a white belt again!