Anniversary/simplified/DJ vowels

For some of you with more experience: (I guess that would be anyone....)

After reading aroung the Gregg sites on the web, and this one, I've decided to go with learning either DJ or Simplified--I'm leaning to Simplified, since I've already got the book, and he extra brief forms don't appear to be too much trouble.

So, in all of this comparison, I noticed something odd--and I'm probably not the first to notice it.

The vowels in Anniversary have marks to differentiate between different "a" sounds, and different "o" sounds. The summary of DJS that I have printed off shows the same markings. But they don't appear in my Simplified text anywhere--at least not that I can find.

So, did Gregg drop them, and then find out they were needed---or have I missed something. And if they were dropped, and were needed, should I learn them and use, or go with DJ.

Thanks for your input

(by harpweaver for everyone)