In your case there is no chance for side-channeling or a cold boot attack so there is no short cut. Attacking the encryption on your hard drive would be computationally infeasible. Maybe the NSA would be able to do it, but that is about it. There are two attack vectors for decrypting your hard drive.

The first attack would be on your pass phrase. Your pass phase probably uses English words and uses substitutions like a->@, e->3, etc. Not that attacking your pass phase is easy, but it probably contains less entropy (randomness) than the 256 bit AES key.

The other attack would be against the AES key. There are no short cuts here and you would have to try every possible key in order to find the right one. This is not an easy task. To put it into perspective there are around 2^256 atoms in the universe. That is essentially playing the lottery where you have to find one atom in the entire universe. You can keep trying, but it you would have to be [nearly] infinitely lucky. This is not going to happen.

Even if a quantum computers become a reality, the effective strength of the key is only change from 2^n to 2^(n/2), and a 128 bit key is still considered strong enough.

The quickest and most reliable method to crack this encryption is the rubber hose method.

After doing further research it looks like the features are fairly comperable for the PGP Encryption software and Truecrypt.

Do you have an opinion on which one you think is better?

I tried truecrypt, and I love it, I like it better than PGP, thank you for the suggestion.