The original Science Centre is an icon of Canadian post-war architecture. Completed in 1969 and designed by Raymond Moriyama, it's Brutalism at its best: organic, raw, and at home in its landscape - evocative of an ancient ruin sprouting out of the forest. The original design has been somewhat compromised by unsympathetic additions over the years, but it still holds up.
The Snohetta design is competent enough architecture, but is placeless, generic, and devoid of context. It could just as well be a shopping mall in Miami.