Nickel and Palladium both form complexes of the general formula $\left[\mathrm{M}{\left({\mathrm{PR}}_3\right)}_2\mathrm{C}{\mathcal{l}}_2\right]$. The ligand  $P{R}_3$is a phosphine such as triphenyl phosphine $\mathrm{P}{\left({\mathrm{C}}_6{\mathrm{H}}_5\right)}_3$. It is a Lewis base. Among these two compounds one is paramagnetic but another one is diamagnetic. From this it can be concluded that

Both complexes are square planar and can exhibit geometrical isomerism.

Both complexes are tetrahedral and do not exhibit geometrical isomerism.

Nickel complex is square planar that can exhibit geometrical isomerism while palladium complex is tetrahedral that cannot exhibit geometrical isomerism.

Nickel complex is tetrahedral, do not exhibit geometrical isomerism, while palladium complex is square planar that can exhibit geometrical isomerism.