RE: 2105 or 2610
2105 appears to be gone, but some clubs still fly it. SSC is extremely popular in some areas, but it hasn't caught on everywhere. 2610 is still going strong, but has faded in some areas. There are also pockets of scale combat pilots that fly by their own rules.
Best bet would be to ask around in your area to find out what's most popular.
HTH,
D