Both pretty bad for gaming, but the 5500 is slightly less bad.  
For under $100, as you'd see from a search using "video", a new Radeon 9600, used Radeon 9600 Pro, and used Geforce4 ti4200 are the top 3 choices.  A ti4200 beats a 5600, dominates a 5500, and stomps a 5200 into a whimpering pile of broken silicon.