There have been discussions in these forums about whether U.S. skaters should join and compete within ISI or USFS (sometimes called USFSA). I think the dominant conclusion has been that ISI is more recreational and fun, but USFS is more appropriate to serious competitors.
Do some of you compete in both?
ISI's Recreational Ice Skating magazine mentions some Synchro teams that compete in both. I'm not a competitive skater, but perhaps this makes sense for serious skaters who do, if both clubs are present in their area. There is a small number of competitions that skaters can compete in within one organization, in any given geographic area. This gives them a chance for more practice at competing. I think ISI competitions may be a bit cheaper than USFS competitions.
(For skaters who need to join clubs to get enough ice time, joining multiple clubs, even multiple chapters at different rinks, often makes sense.)
Of course, it is a nuisance for their coaches, who would have to join and be trained for and certified by both organizations.