because he looks like more of a icon in that outfit than i feel heather did. ala capt. america and captain britain, i never fet heather looked as dominant and a symbol for the team and country as mac did, but again, thats my opinion.
and as far as how heather has been written since she has had a child i think she has been in the total of one issue, and her relation with her child has been summed up as "we better stop and pick up our child on the way to outer space"
she has "yet" to be written that way, "yet" being the key word. because i feel heather feels very strongly about family, and the last thing she would do is leave a child in someone elses care while she was out saving the world. but again......my opinion.