the story, or the one i heard, is that ST worked with the
israelis for awhile on the design of the weapon, then decided to go
seperate ways to develop it... that is why they look kinda similar,
but are actually 2 different weapons.
the SAR bolt carrier, for those who had done NS before, will in
fact look very, very familiar...
as for which weapon is better, lets just agree to disagree on that

as for whether ST imports stuff... well, depends which ST u're
referring to... STK mostly manufactures under license and exports
stuff through Unicorn, their marketing arm... i heard also that
this is the same pple who are known to have some rather unsavory
clients but in the business world, money is money...
as for importing for mindef, i think not... mindef deals direct
unless ST has a role in customising, modifying the system for
them... then ST is operating under license from the original
dealer... kinda like a partnership.
mindef has also made it very clear on some occassions that ST does
not have a monopoly in supplying systems to the SAF... if they
can't deliver the specs, mindef will shop elsewhere.