AWD vs. FWD - Pros and Cons

I have a 1996 Subaru Legacy and I saw that I have the option of switching the AWD device off so that the car would be Front Wheel Drive. Would this be a good choice for the FWD to be set for long-term. I am doing this hoping I can get better gas mileage. Is this a good choice and what are my pros and cons of doing so.

Thank you,

Malek