I have both, and Ella generally prefers to face out, she certainly doesn't talk any less when facing out and she will not sleep facing me! I have to turn her around when she gets tired! That said we have a Quinny and the main reason she doesn't like facing me is that it doesn't sit upright enough when it is rear facing (something for others to consider when buying one)
One of my criteria when choosing a pushchair was that is faced me, but now she is older I generally use the buggy where she faces out. In all honesty I think this study is rubbish - yes it is better to be able to interact with your baby, but how much time do they spend in the pushchair? Less than 10% of a day, not interacting while they are in the pushchair isn't exactly going to lead to them being 'emotionally impoverished' is it! Besides I still talk to Ella whether I can see her or not, I just look like a mad woman talking to myself!