Have you read DadDude's detailed review of Singapore Math (Earlybird Kindergarten level):
http://forum.brillkids.com/teaching-your-child-math/review-of-%28singapore%29-earlybird-kindergarten-math/ I don't think I can do a better job at reviewing it than he did

except to tell you that I have been doing both Singapore Math and Jones Geniuses with Ella. I think they complement each other rather well and emphasize different aspects of learning math - at least at the kindergarten level. Your son may already be beyond the Earlybird level in Singapore Math though and I haven't seen the next level book yet to be able to comment on it.