Yep, if you have 2 similar fluid choices and 1 has the JASO spec, then I would choose it. But, IMO, Mercon-V, ATF+4 and DexronVI are quality ATF(finally). To think our domestic ATF's have been lacking for years.
Chevron Multi-Vehicle ATF has been tested for performance in Japanese transmissions under the JASO 1A ATF standard. The product will deliver the shifting performance and superior anti-shudder durability which is desired by Japanese and Korean automakers.
Castrol Transmax® J meets the requirements of the Japanese JASO 1A standard for automatic transmissions and is also approved by GM and Ford for use in all applications requiring a DEXRON®-III or MERCON® approved ATF. Consistent frictional properties improve driver comfort. Very long antishudder durability for comfortable gear changes without noise, vibration or harshness.
For the anti-multivehicle and anti-universal ATF crowd(4mb download):http://epubl.luth.se/1402-1544/2005/28/LTU-DT-0528-SE.pdf
More recently, the International Lubricant Standardization and Approval Committee (ILSAC) ATF
subcommittee has started work on comparing and merging the different standards since it has been
demonstrated that it is possible to formulate fluids that comply with both the American and the Japanese