the reason Kodak recommends the same dev times for 200 as for 100 with Tmax100 is because the film has some latitude. Yes, you might lose some infitesimal shadow detail, but developing longer costs you more in lost highlights, IMHO. Consider that the longer you let the film sit in the developer, the more of the highlights develop to black on the negative. If you don't mind losing more highlight detail than you gain shadow detail, dev for longer with 200 IE. If you want to keep as much detail in your highlights as possible, don't.
To start with, shooting 100 at 200EI just underexposes the film by one stop, which isn't much in reality. And often, when dealing with a scene with bright light and dark shadow, something has to give anyway. I try to expose for the details I want to keep, i.e. usually shadows, and don't worry about highlights unless they are the specific detail I wish to preserve.
It's all personal taste anyway. There is nothing that says a technically perfect average exposure is the best one for every image. Yes, we all know the Zone system is great for learning how to capture as much information as possible on the negative, but I'm purposely cutting information out of the scene every time I frame the subject, and even more when I crop. Why would I carefully frame to capture only the portion of the scene I wish and yet insist on exposing to capture the most data rather than just the light I want?
