You should research UA and SQ websites. My gut feeling is the SQ's program is not very good.

In the late 90's, there was a United Shuttle division. UA only gave flight miles to those flights with no minimum amount. Lufthansa, however, awarded 1,000 miles to all UA flights, including Shuttle by United. I only had some orphan miles on LH but soon afterwards, I started building up LH miles by flying Shuttle by United. So check carefully UA and SQ.