I'm a little late to the discussion, but I thought I'd put in my 2 cents worth.
I am not (yet) a member of the 501st, but to me the 501st are costumers, and cosplayers. However, at the same time, the 501st is something else entirely. The 501st, is the 501st. Sure, as costumers, you make and design costumes to wear, and try to make them accurate to their source. As cosplayers, you wear the costumes, and let yourself become the character.
But, with the 501st there is a difference, just as with other similar groups. The 501st has a goal, and a purpose. We are dedicated to not just make a good costume, but to be part of something bigger. To create a costume, to wear it, and know that you have put in the effort, to not just make, assemble, or organise it, but to be part of a group. And as a group, the 501st, is not just about having an awesome outfit that you can wear to conventions, but it is also about helping people, and making people happy. Raising money for people, and doing what they can.
There is a distinction between a police officer, and people who try and stop crime. A police officer IS a person who tries to stop crime, but a person who tries to stop crime, isn't necessarily a police officer. Police officers have standards and authority. Rules, and a distinct purpose.
The 501st, are cosplayers, and costumers, but the 501st is also something in itself. Not just pieces of clothing, a uniform or armour, but a whole community that we are part of, with a goal, and a purpose.
If you don't like the phrase "cosplayer", that is up to you. Just as some police mightn't like slang phrases like "cops". But at the same time that you don't like it, it IS a term that defines what you are doing. You're part of the 501st. You do costuming as you put together your outfit to fit standards, yet you are also cosplayers as you wear the outfit to pretend to be a character in a costume. You are part of the 501st, as you do that as part of a larger community, for a purpose.
