Why not look at doing both?
If the numbers are there for both, and there are people willing to organise each of them, then do both, if not do the most popular one.
As long as the schedule works out, there's the posibility of getting enough people who can do one or the other, or even both of them.
I know for some people the cost will be a big factor in whether they can go or not, but for others it will simply come down to 'when and where'. So if the discussions and 'arrangements' keep going for now untill it gets to the point of actual money being spent, then why not look into more than one option?