Both may be signing some nice contracts we can't afford. However, it's a deep WR free agent class and with Gallup's injury I wouldn't assume we're out of the market there. Wilson looks to be a player on the rise, but up to this season he had 22 career catches so would think he's not as coveted.
If I had to retain 1 and it was a difference of a few million per year I would go Gallup. Despite the injuries Gallup has done more and let's not forget Wilson had an injury history since he entered the league for those concerned about Gallup. I know we are all excited about a few big games from Wilson and would like him back too, but Gallup is the choice.