I will disagree here. I found ChatGPT better at English <-> German translation than DeepL. Especially at translating slang and online speak where DeepL would shit the bed.
I found that specifically when it comes to proper flow and grammatical rules, chatGPT and other LLMs tend to break down. Certainly when translating from English to another language. From another language to English often goes a lot better, but that really depends on how much training data in that language the LLM has been trained on.
German would be one of the languages where LLMs likely will perform fairly well, as it is one of the languages that LLMs training data often contains quite a lot of.
With DeepL if I am using it to translate a language I am not too familiar with and can't validate the outcome as well I therefore will have more trust in its translation. Because I know that the languages they support are actually specifically implemented for translation reasons.
I can't say for en <-> de, I can read both without problem. But for Japanese DeepL is much better, often times the tone from gpt4 are little bit "rude"/direct or "weird" in en to jp, deepl is as good as an example sentence they would put into a textbook. For jp to en, most gpt4 or any llm is much superior, because you can ask follow up questions on certain slangs, or anything that's not very clear.
German would be one of the languages where LLMs likely will perform fairly well, as it is one of the languages that LLMs training data often contains quite a lot of.
With DeepL if I am using it to translate a language I am not too familiar with and can't validate the outcome as well I therefore will have more trust in its translation. Because I know that the languages they support are actually specifically implemented for translation reasons.