If you're arguing about the best #25 in Falcons history, it's a short debate with only one answer. Save yourself the time and embrace Scott Case.
Case is simply one of the best Falcons defensive backs ever. He was known for his physicality and aggression, and during his eleven seasons in Atlanta, he put up a combined 30 interceptions, 7.5 sacks and gobs of highlight reel hits. The Falcons' defense was hit or miss throughout much of his tenure, but he was a key player on some very good units, and is a legend for good reason.