But if you have 20, no matter what the dealer is showing, the correct play is to stay. If the dealer turns over 21, there isn't much you can do. You obviously can not predict the future.
Edinson's hand wasn't that strong, but he still was gambling that he'd be more valuable after a full healthy season then he was at that time. No matter how that turned out, the decision was still based on whether he felt like he could pitch better than he had in the previous season.
This past winter, there was no reason for him to think he'd have a worse season then one which didn't even start until July and still featured it's ups and downs.
That his gamble hasn't paid off doesn't make the decision better or worse.
It's really the same logic on the trade. Both Edinson and Hamilton had their virtues and risks associated.
Just because Edinson's risks have come to fruition and Hamilton's haven't yet doesn't make the cost to assume those risks and virtues at the time any different.
That said, I'm glad he turned it down, because if he doesn't improve, there's nothing that keeps him from being cut.