Translation:Dylan and Gareth are as good as their friend.
There are two words meaning "so, as", cyn and mor. In the literary language cyn is generally used before short adjectives with the ending -ed and mor with longer adjectives.
cyn ddued â'r frân (as black as the crow)
cyn wynned ag eira (as white as snow)
mor ddiddorol â gwylio paent yn sychu (as interesting as watching paint dry)
However mor is most often used in all cases in the southern spoken language.
mor ddu â'r frân
mor wyn ag eira
The "cyn" bit remains in certain common adjectives, however, and they're often used.
cystal â'r llall (as good as the other one)
cynddrwg â dy blant di (as bad as your kids)
cymaint ag elifant (as big as an elephant)
cyn lleied â llygoden (as small as a mouse)
You could of course use mor for those informally.
mor dda â'r llall
mor ddrwg â dy blant di
mor fawr ag elifant
mor fach â llygoden