I hear these two phrases quite a lot but haven’t worked out what the usage pattern is yet (if there is one). Are they interchangable or when you are saying something is finished would you use one over the other depending on content/tense
cwpla and gorffen are verbs, but ar ben is an adjective, so while both can be used to express finishing, you need to build the sentences a bit differently: Dw i wedi gorffen fy ngwaith. - I have finished my work. Mae fy ngwaith ar ben. - My work is finished.