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COMPASS or DREIDING forcefield??

Hi all,
I am calculating the potential energy of Poly Vinyl Alchohol using forcite module of two different FF(COMPASS & DREIDING). I am getting two different potential energy values of -5355 and -2262. Apart from this in Dreiding FF I am getting H-bond energy, which is missing in COMPASS. 
Can anyone explain this, and suggest which one I should take if I calculate interaction energy AL metal surface?
CarstenCarsten (Accelrys) 
There is not absolute zero for force fields. Not even within the same forcefield. Therefore, energies differ.

Normally, only energy differences are of interest. For example the interaction energy of the Polymer with the Al surface.

I would use COMPASS I think because I would expect that it described the polymer much better.

For COMPASS it is assumed that the vdW interactions and the electrostatic interactions describe the Hydrogen bonds accurate enough.

Please keep in mind that DREIDING does not come with charges.

In the original DREIDING paper is is stated:
In this paper we either ignore charges or use the Gasteiger estimates for charges.

Without charges a separate Hydrogen bond potential is needed to describe Hydrogen bonds properly.

Ideally, you always should compare with experimental or QM results to see

Thank You Carsten.