so back to the original question: depends on your priorities. Max financial return - the chrome ES is about as collectible as Pentax gets and should bring a good price. However, should you ever grow nostalgic for it and want a replacement, you'll have to hunt a long while and pay good money. And it may not be in as good shape as yours is.
The SP II won't bring you a lot of money, but then it is easily replaced when you grow nostalgic
I would keep the ES and send it to Eric, and enjoy it for a long long time. Unless I was hard up for cash for film, I don't think the hassle of selling the SP II is worth the money, so I'd keep it also
(spoken like a true camera accumulator...)