ALL helmets must meet the same safety ratings. After that it is fit/feel/look.

My personal experience is that my newest helmet is my favourite (and also the most expensive). I like the way it looks and I LOVE the huge vents that it has. If his commute is long, I would look for one with more/bigger vents.

Brand/model is irrelevant to me, because like saddles, everyone has a different idea of what is comfortable.

Look for deals on last year's models. They are the same helmets for a fraction of the price (I love buying "last season" stuff.