Abosolutely with EGDR. I did the course with Bristol: brilliant notes & CD ROM, fantastic instructors, very helpfull, I passed first time (
) Of course this is my personal & subjective opinion.
The only reference I have about OATS was a peer student who attended our course for a couple of days: this person had been with OATS and didn't know the difference between QNH, QFE & Standard Pressure: I wondered how this wasn't noticed by the instructors at OATS
On the other hand I'm sure there're lots of ex-OATS with very positive experiences as well.
Don't expect a definitive answer to your question, at the end of the day, remember this is only a forum where people (at the best) tell the story the way they lived it.
Good luck!