In general, the strength of a sigma bond is determined by the overlap of atomic orbitals between the bonding atoms rather than the specific hybridization involved. Therefore, it is not accurate to say that a PP sigma bond is inherently stronger than an SP sigma bond or vice versa.
The strength of a sigma bond depends on factors such as the overlap of orbitals, the bond length, and the types of atoms involved. A stronger overlap of atomic orbitals leads to a stronger sigma bond. Additionally, shorter bond lengths generally result in stronger bonds.
However, it is worth noting that different types of hybrid orbitals can have different spatial distributions and degrees of overlap. For example, in an SP hybridized bond, the orbital lobes are oriented in a linear fashion, allowing for strong overlap between the orbitals. On the other hand, in a PP bond, the orbital lobes are oriented parallel to each other, which can result in weaker overlap and potentially weaker bonding.
Ultimately, the strength of a sigma bond is determined by the specific molecular and atomic context, including the types of atoms involved, their hybridization, and the specific geometry of the molecule.