I've slaughtered both goats and sheep. Good stuff if properly processed.
My first experience with mutton was a "leg 'o lamb" out of a meat market. The wife was on a "Passover" kick and wanted some lamb. After THAT experience, we didn't buy mutton for MANY years! It was nasty.
I've slaughtered rams, ewes, nanny's, billies and wethers.
They were all good, but the wether was the best!