b3lyp and b3pw91 is not a basis set...learn more quantum chemistry

....and google is your friend

B3lyp and b3pw91 are functional and lanl2dz is basis set.you can use lanl2dz for 3d metal

Both B3LYP and B3PW91 are exchange-correlation functionals. These two functionals follow the "structure" of the hybrid funtionals, suggested by Becke, where 

E(x) = 0.8E(x)(LDA) + 0.2E(x)(HF) + 0.72 DELTA E(x)(B88)

and

E(c)(B3LYP) = 0.19 E(c) VWN3 + 0.81 E(c) (LYP)

E(c) (B3PW91) = E(c) VWN5 + 0.81 DELTA E(c)(PW91)

As you can see, the differences between both functionals appears in the correlation energy contributions (E(c)).

In B3PW91 only the local contribution is considered in the E(c).

I think this answer your question about the differences between the funtionals. . 

Can I use B3PW91 functional for dispersion interaction using g09 software.

Péter Szabó , congratulations for the 2015 most useless answer award!