This is a pretty standard question that I've seen 200m runners deal with. It comes down to: what are your weaknesses in the 200m that you need to improve? If it's speed, then 100m might be better to focus on as a secondary distance. If you're gassed by 120m like me, then running the 4 might be best to build up your speed endurance. You could always do a mixture of both of course. I know lots of sprinters in my club do a mix of 1,2, and 4 training.