PE:
Crude Protein 69.5% min.
Crude Fat 8.35% min.
Crude Fiber 2.75% max.
Ash 5.5% max.
Other 13.9%
Hikari:
Crude Protein 10.5% min 70%
Crude Fat 1.0% min 6.67%
Crude Fiber 2.0% max 13.3%
Moisture 85.0% max 0%
Other 10%
Above is more of an apples-to-apples comparison, calculating the approximate percentages with dry weight. Both brands offer comparable levels of protein. PE seems to offer a little more fat and Hikari seems to have a lot more fiber.
PE is definitely more fatty, IME. I feed both types of Mysis daily. Some of the fish refused the PE at first, but now, a lot of them prefer PE. The smaller fish prefer Hikari, but most of them seem to like both equally.