I have PCOS as well. Atkins worked for me in the past (though I never stuck with it for very long). I started on Atkins again in Jan and lost a lot my first week and then lost about 3 lbs in a month despite being very strict. I just started Ideal Protein and like it so far. I too, don't always have the time to cook, and IP is a lot easier with that because you only cook one meal for yourself per day. Some of the packets do require boiling water (chili, spaghetti, and oatmeal) or light cooking (pancakes, crepes, and omelettes), but for the most part you'll just need water and the shaker. The biggest difference is probably portions, with Atkins you can almost eat as much as you want, but IP is low carb and low calorie so the IP meals are rather small (they encourage snacks and unlimited lettuce). But honestly, they're both ketosis diets and ketosis really suppresses my appetite so it's more of an effort to make myself eat. I've only been on IP for a few days so I can't compare the results yet, but there's been a lot of people who've been successful on it. I think IP has better transitioning phases to go back to more normal eating. Also, exercise is much more limited with IP because of the low caloric intake, so that could be a deciding factor as well, whether you exercise a lot or not.
Either way, a ketosis based diet is the best for PCOS in my opinion, because it really counteracts the insulin resistance and once you loose a bulk of the weight, a lot of the PCOS symptoms should clear up.
I hope that helps!