I think I'm the one that has brought up this discussion several times as to which program people would be using for the guilds. As of now, none of us know what program we'll be using in the Guild Competition. This is just to get a feel as to where the community is currently at with how comfortable they are.
You don't particularly need to post anything like why your more comfortable with one program over another, but knowing who is comfortable with what will help the guild leaders make their decision of picking members when that time comes around.
Again, it's not like 1 guild will be XP and the other will be VX. It could very well end up being XP vs XP or VX vs VX or XP vs VX. The decision of what program will be used will be made after the guilds are created.