Difference between the MSI and Sapphire 7770 is that the Sapphire is of (IMO) higher quality and a higher memory clock. The manufacturer depends on personal preference, but just know the Sapphire has a higher memory clock which would make it faster.
The 7750 is a slower GPU that doesnt have as many stream processors. All price points are around the same.
Out of that list, I would take the Sapphire 7770.