they are all much the same if you are comparing reference cards.
there will be very little difference.
reference cards is the type of cards that uses the same PCB design as AMD and Nvidia originally used to make and test there GPU they have made.
that same design has been made by all other companies that makes graphic cards.
but some is not a reference design.
some has changed the design to make a better card.
like adding more RAM, addning Full-HDMI support, bigger coolers, new power design or/and smaller PCB.
so it is up to you what you need and what you will pay.
MSI might have a AMP edition witch will have better power design and cooler. great for overclocking.