Here are the base stats:
Muk
Hp-105
Attack-105
Defence-75
Sp.atk-65
Sp.def-100
Speed-50
Weezing
Hp-65
Attack-90
Defence-120
Sp.atk-85
Sp.def-70
Speed-60
Muk has good Sp.Defence and good HP to back it up.
Weezing however has good defence, but not enough HP to back it up.
And Muk has better attack than Weezing, so I would suggest Muk instead of Weezing.
Hope I helped.