As per the data provided above, Latin is considered to be the best scaling language subject. If French Extension scales approximately the same as Mathematics Extension 1, and assuming Latin Extension scales better than French Extension, then Latin has some seriously good scaling. Biology is not the best scaling science subject, particularly when considering subjects like Physics and Chemistry, which scale higher than Biology.
With that being said, scaling should not be the primary consideration with respect to subject retention. Keep in mind that you can achieve a high ATAR with any combination of subjects, meaning that your focus must be on your performance across your subjects going forward. Additionally, the higher the marks you achieve, the less significant the effect of scaling becomes. This brings the question: Which subject are you more confident in with respect to academic performance/potential?
I usually try to respond in an objective manner, but having had a look at the Latin Extension 2020 HSC exam paper, I felt relatively positive about Latin Extension as a subject (which would imply the same regarding Latin Continuers). I personally feel like I would be able to achieve a band E4 in this subject, provided I am determined and study regularly. Also, the fact that I have an interest in languages, as opposed to my lack of interest (and being rather incompetent at science subjects), would make me lean more towards keeping Latin Extension. I would therefore suggest you keep Latin Extension and drop Biology.
I hope this helps!