The BIG Difference is that here the bikini woman can choose to cover herself up, while the woman in burqa may get stones thrown at her if chooses to go around wearing a bikini. To sum up, even wearing a tiny bikini can be an expression of freedom and feminism. This picture is juggling with logic to back up the idea that women in islamic cultures aren't seen as inferior to man, but unfortunately they are and that's why some women, for example, get acid thrown in their face if their husbands see them looking at other men.
I think BURQA's meaning is "if you wear a burqa because of your religion, for me wearing only heels and underpants is also my religion. I respect yours, respect mine." That's why Gaga sometimes wear burqas.
Difference would be that in Western countries they can be covered or uncovered if they want to and in SOME Arab countries they can be beaten up or even condemned to jail if they don't apply to the dressing code.