The VS series is based on CWT's GPA design, which is a very low end design and uses JunFu caps, which aren't very good. Low efficiency is another disadvantage.
The GPA series only goes up to 500W, so Corsair is again inflating the wattage number on the label.
It is in fact worse than the CX series.
The CMPSU-VX 550 is definitely not new, probably the reason it is not available to you is that it has been discontinued.
Builder Series™ VS450 — 450 Watt High Performance Power Supply
VS450: the entry-level 240V power supply with high-end features.
The Corsair VS450 is a great choice if you’re building a home or office system with lower power demands, but you still demand the compatibility and reliability that Corsair is known for. NOTE: Available in the Asian market only.