The GOTY edition includes the Red Hammer campaign, while OFP: Resistance doesn't. If you already have Red Hammer, then this is irrelevant.
The GOTY edition installs OFP version 1.85, while OFP: Resistance installs OFP version 1.75. Of course, you can upgrade either of them to the most recent OFP version with the latest upgrade patch released by BIS.
The third CD of the GOTY edition contains 18 audio tracks of music from OFP, playable with WinAmp, Windows Media Player or a similar CD audio player. However, you can obtain these tracks and more by extracting the audio files yourself from your existing OFP CDs. Details can be bound in this FAQ item.
Other than the above, however, it's the same game with the same features.