As someone who has played Stall for over a year, testing both Chansey and Blissey, here's what I got.
All of the posts regarding Gengar hold little to no water if you are actually intelligent when using Chansey. As long as Chansey has Softboiled, SubSplit Gengar will NOT always defeat Chansey. PP stalling Focus Blast is quite easy, and it becomes simple when regarding the 70% hit ratio. Almost every battle with Chansey I've been in vs. a SubSplit Gengar I've just PP stalled Focus Blast, and then bring in something to resist Shadow Ball and go from there.
Another note on Gengar is that a good 75% of them that I see are SubDisable, which screws Bliss over anyways. Well, according to the above logic it screws over Bliss, when in reality Bliss can PP stall either Gengar just as easily as Chansey can (and with WishSoftboiled it's not even a competition vs. SubDisable Gar).
That being said, residual damage is very important in the long run, any player will tell you that. However, the sheer bulk of Chansey EASILY outweighs the momentum you might gain from Blissey.
HOWEVER, a big thing here is that, on most stall teams (and by that I mean, yknow, all stall teams) a dedicated Spinner is used. A good chunk of Stalls are weatherless, sun, or rain, with only a few being hail or sand. If you are running Chansey on a non-damaging weather stall team, it will FAR outclass Bliss.
A big thing is that people often overlook just HOW much bulk Chansey gets. It's the difference between Psyshock 2HKOing and not 2HKOing. Even very strong physical hits (+4 Landorus EQ out of sand) can be taken by Chansey. Blissey may have the ability to abuse WishTect better, but with all the sand flying around, this is even less useful.
Overall, even without spin support, I found Chans to be more useful than Bliss due to it's staggeringly good physical bulk, and the fact that both defenses can be boosted so much with Eviolite (max def/sp.d is spectacular).
So I'm in the Chansey crowd.