What is an OBA
OBAs are optical brighteners that are added to the paper coating to make the paper appear whiter than it actually is. The down side is that the OBAs fade quickly leaving you with colour shift and is undesirable in Fine Art prints.
The reason the OBAs are added is mostly because natural paper is quite yellow especially when compared to your display. This will affect your colour choices and can be a problem if you need very pure colours to pop when you print them. Most manufacturers will use the purest pulp in their paper to minimise the use of optical brighteners.
Papers made for sale or exhibition should not have optical brightners in them if you want to be assured of their longevity. This will mean your paper will be slightly warmer and this will need to be taken into account during the proofing stage.
Examples
Hahnemühle Museum Etching 350gsm
Notice the warmer white of the paper, there is no OBA in this stock. Click here to get more detail on this paper.
Smooth matt white paper.
This is an example of a paper that could have a high optical brightener content, notice the almost blue hue to the paper. Some manufacturers have developed their own propriety chemicals to bighten the paper and still achive archival standards.
Conclusion
So keep in mind what the purpose of your pint is going to be, for example should it be for sale to a collector then you want an OBA free paper, if you need to present a design project then the bright white will allow your colour to be more pure and will have more pop. These papers will come in at different price points which will also affect your final desicion.