  We compare ground state energies by variational Monte Carlo of the spin
unpolarized Halperin 331 and the spin polarized Moore-Read (MR) Pfaffian
fractional quantum Hall states at half-filling of the lowest Landau level (LLL)
and the second Landau level (SLL) as a function of small deviations around the
Coulomb point via the finite thickness effect and direct alterations to the the
first two Haldane pseudopotentials. In the comparison we find that in the LLL,
either the 331 state or the MR Pfaffian may be lower in energy depending on the
deviations. In the SLL, however, the MR Pfaffian is consistently lower in
energy except for large deviations. These results suggest that even under
moderate deviations in the interaction potential (through various physical
processes such as finite thickness, Landau level mixing, etc.), the MR Pfaffian
description is more energetically favorable than the Halperin 331 state in the
half-filled SLL (i.e. $\nu = 5/2$), consistent with recent experimental
investigations.
