I think what everyone means to say is no one really has the answers you're looking for. Google and Bing work slightly differently, you can see that running a few results through each, but the differences are pretty fine details amongst a lot of secret algorithm and code the search engines protect and we can all only guess at.
I assume a general consensus is that if you get good results on Google you'll have decent result on the other, they both basically want the same thing, but there will be a few thresholds different that throw things out. Like maybe (grasping numbers from thin air purely as an example) Google thinks a 7% keyword density is OK but Bing thinks 6% is OK and anything over that is getting spammy, however you might need that 7% density to get your top ten on Google because others have it, so for that keyword it's impossible to be top ten on both, they will each have slightly different evaluations of social network value, what constitutes good backlinks and bad and so on. It depends on so many potential variables it's impossible to give you a straight answer, the best you can do is fiddle around with small details bit by bit and monitor your results closely to see what might help, or if you've tried everything you can think of look at different keywords.