IMO Blissey is superior. She can pass up larger wishes than Chansey, and has an actual Special Attack not to rely on Seismic Toss all the time(and IMO I'd rather choose P2 for Eviolite walling, tyvm)
For best non-Bliss/Chansey wall, obv Lugia. Multiscale, fuck off bitches. Being able to outspeed non-scarf'd pokes = fuck off I Recover to multiscale INURFACE.
(Also why isn't Forretress in the poll...?)