There should be no difference. I worked with a number of openly gay/bisexual people in the RAF; I also remember the occasional sex change that brought some hilarity (Benson late 90s). Your only problem will be if you try to use your sexuality as a tool to gain advantage. I remember when we first took on female pilots where there was a very small minority that decided to either play the sympathy or victimisation card. This was a real pity as the majority of the girls could easily hold their own.
So, back to gays. They have been around the armed forces for a while (way before the rules changed in 1999) and most people just didn't have an issue. As for those who advise you to keep things quiet, I must ask why? Just behave like an officer.