My perspective is that its worth crediting to Krisflyer if you are also collecting miles by credit card.
Several local banks only let you transfer miles to Krisflyer or Asia Miles.
Once you have a pool of miles you will find that Krisflyer only releases long haul first and business seats to their own members, and then not enough to satisfy demand. Plus SQ offers a 15% discount for online redemption bookings for KF members.

So if you are collecting miles for luxury travel and maximum flexibility go for Krisflyer. If its just for status then its less important. Hope that helps.