GB may give you the highest price, but likely only under certain conditions. If you are a new seller (little or no feedback) potential bidders will be reluctant to be the first to buy from you. . .and initial prices are likely to be limited by that reluctance. The best prices are realized by those who have high condition guns and many, many excellent pictures at all angles. Sometimes supporting information about the type of gun, any unusual factors (scarcity/number produced/etc.) explained, can help too. If you don't have A+ feedback history, or any at all, and aren't great at pictures and info, and if your guns are not in high condition, you may be disappointed by the auction prices. You also have the hassle (and cost) of having to find an FFL to ship the guns for you. Auction sites can be great, but they will not always automatically produce the best prices for the least effort. Good luck.
Jeff
SWCA #1457