Differences among reference GPUs from different manufacturers

I was looking at the various reference 290s available and was wondering if it makes a difference what company you go with when it comes to reference cards? HIS, gigabyte, asus... any variations worth nothing among any of the brands?

Thanks

AFAIK reference layout is reference layout. Some use different RAM chips that clock better, but other than that every thing is pretty much in the same place. Comes down to cooler and brand preference really.

If it's a genuine reference card, last time I checked they were all identical and made by Foxconn. Get whatever "brand" card has the best warranty.
If it's a reference PCB with a non-reference cooler, then there are differences.

EVGA 780Ti SC ACX is a reference board according to EKWB Or am i understanding you wrong... reference board is reference board regardless of cooler. Reference board doesnt mean they have the same RAM, or use the same caps etc. Just means they are laid out the same, and still a reference board. Pretty sure all AMD reference PCB's have AMD stamped by the PCI-e slot, and non-reference do not (My card is a non reference PCB, and is INCHES longer than a reference 270X, just over inches on the PCB, 11.5 overall)

Do not confuse a reference card with a reference PCB. "card" means the whole thing including cooler. Reference cards are all built by Foxconn and are identical.
Reference PCBs are built by anybody to AMD/Nvidia's design specs, then populated with whatever caps, ram, etc that manufacture wants to use.

From a waterblock standpoint either one can be called reference, as the block mounting is the same. From a performance and parts-used standpoint they are very different.
You can also find reference PCBs that are not marked amd, as amd did not have the PCB manufactured. Gigabyte and sapphire are two brands that often use the reference PCB design but manufacture it themselves.

Gigabyte is often making nearly reference PCB with 1 additional phase or some parts slightly moved couple of mm left or right. The only really changed PCB are in Superclocked series.

Sapphire makes most their cards on reference design and is using reference parts for power section etc ( at least all their cards that I saw were exactly like AMD reference but made by Sapphire so without AMD logo on the PCB ).
The same most other manufacturers are not changing anything even if they manufacture PCB then you can find all other parts from regular reference cards. Most are simply using better cooler, add 30MHz to core clock and call it super something series.

Non reference cards like better PCB/VRM and better cooler are almost only EVGA Classified, Gigabyte Superclocked, ASUS DC2/Matrix and MSI Lightning ( all Gaming etc are reference ). There are some other series like Sapphire Toxic but these are not always modified, all depends from used chip.

HIS is using reference PCB in all their cheaper series. I have no idea what with R9 290/X. They used to have 1-2 cards from the top series on their own PCB design but usually almost not available in stores and expensive.

Right now all cards are using the same memory or specified for the same clocks and voltage. Most cards are on Elpida chips and only small part on Hynix. Samsungs are almost not existing in high end graphics cards. I saw them only in some selected EVGA Classified.