Power up Chansey or save for Blissey?
After the buff, Chanseys have an interesting and viable defender role, but with Gen II on the horizon and Blissey's looking to be pretty powerful, is it worth powering up a Chansey for using now or should we be saving candies for the future release of Gen II?
Answers
Make it your buddy so you can do both?
Even if Blissey is a powerhouse, she won't do you any good whatsoever if you can't power her up. Having a pre-powered Chansey will be useful.
So unless you think there's a reasonable chance you'll hatch/catch a better one before gen 2 (which who knows how long it will be) you may as well enjoy it now (power it) AND walk it for candies so you can evolve it in gen 2.
That said, the alternative is to just sit on the STARDUST. Candies aren't the issue as you'll need to both power and evolve, but stardust can be used elsewhere. What if Blissey comes out with a garbage moveset?
If you're reading about chansey being unkillable in the time allotted on those click bait sites they are false. They are very annoying for attackers though, especially when put in the right gyms(with trash under it, multiple chanseys, snorlaxes above it)
I would rather fight a 2500 snorlax than a 1250 chansey. It is a deterrent if the attacker has fought them before.
Just keep enough to be able to evolve, moveset won't matter on Blissey and it doesn't on Chansey either.
However I disagree about Chansey being all that great as a defender, my Rhydon 29xx took down a 1200 Chansey in 40 seconds and you don't even have to dodge; not even Hyperbeam has any power on Chansey.