it's just like the essay writing, initially I wanted to put as much information in one essay as possible, but later on I found that it is not a good idea to cram reader's head with too much information, you will lose your focus. similarly I believe recommendations should convey messages consistent with those in your essays. Recommendation letters should be the third party view strengthening what you said in your essays. In this sense, I think it is good to pick two or three major strenghths and let each recommender focus on one or two. If there is still space to talk about other virtue, then go ahead.