Why is my new SSD two times slower?
If your SSD is slower using random data and fast using simple data like ones you have most likely an SSD using a SandForce chip. This chip uses online compression for all data. The maximum speed is only reached for data that can be compressed well.
The default test method of CrystalDiskMark uses random data which can be seen as the worst compressable data. Therefore you are not getting the benchmark results as expected.