I've owned both. Silverball Mania has great artwork. Center shot was kinda fun. Shouldn't be too tough to sell when you are done with it.
Black Pyramid is terrible. After you have it for 6 or 7 minutes and realize it's terrible nobody will buy it.
I am admittedly a DMD guy but I do like an older game occasionally. Silverball came out in 78, pretty cool game for that time. Black Pyramid in 1984? Couldn't do any better in 1984?