All this split represents is an argument between two groups of miners as to how the scaling issues that bitcoin is having should be solved. One group think it should be solved by increasing the block size and the other group by increasing transaction fees. That's an oversimplification but essentially at the core of the disagreement.
If the majority do not go one way or the other and bitcoin does split into two coins then the market, meaning every day users of bitcoin, will decide which has more value.
If most users want the original bitcoin then they will sell the other coin to buy more of the original. All that selling of one coin and buying of the other will lower the price of the former and raise the price of the latter.
Hope that makes sense.