This word has cogantes and is related to the Slavic word 'sok' and the English word 'sap' :)
Yes they are in South Wales, slightly differently in North Wales, here's a link to a video which explains the difference. The rest of the videos in the series are worthwhile too. https://www.youtube.com/watch?v=Dqv1geIlfFI&list=PLz6oFM0_IszwxmU7dMcGQClZ5zMwX2EdY&index=3
Though from what I understand from the video, the two words should be the same in North Wales as well, since they say that u = y. (It's just that in NW those are different from long i.)
In North Wales the 'u' is a more back of the throat sound, so it would be subtly different from the sound of 'y' in the word 'sydd'.