What is the rationale behind disabling Superfetch on SSD systems?
The reason why SSD manufacturers recommend turning off SuperFetch is because SSD's can only take so many read/write cycles to the same sector before performance degrades and SuperFetch will read and write to the same sector repeatedly.
It is not so much that the SSD that will be faster than the RAM, but that the lifespan of the SSD will be decreased. The benefits don't outweigh the cost.