In the past, I had thought of working on Cantonese into written Chinese transcription job. From subsequent research I found out that I could not write fast enough. This is why I still feel comfortable working on Cantonese into English transcription.
The hardest part of transcribing Cantonese into written Chinese is that Cantonese is a language of two thousand years of history. A Cantonese phrase of several words contains rich meaning, and it takes excellent writing skills for transcribers to produce written Chinese with character limit for each subtitle line.
The Chinese subtitles of Hong Kong Connection and other programmes of RTHK are very well written. Transcribers / transcriptionists who wish to work on Cantonese into written Chinese can always learn from the programmes.
As for me, it is better if I focus on Cantonese into English transcription, for I am usually reading English books and online articles most of the time. When I read more well-written Traditional Chinese books, I guess I can do better in Cantonese into written Chinese transcription.