personally i dropped to english standard in year 12 and i ended up topping my cohort whereas in advanced i couldnt even get an a, the expectations not only within ur school but also nesa's marking is lighter, the texts are easier, u wouldn't be expected to write the 4 paragraphs that many advanced students write, etc. overall i would say drop if u feel that u have enough skill/motivation to get a top rank in ur cohort, otherwise as others have said its easy to get dragged down by alignment, scaling etc. also a good reason to drop is to have more time to invest in other subjects, for me a very strong reason as to why i dropped was in order to have more time to focus on 4u math which i picked up, reading a 200 page book and understanding its intricacies is much easier and less time consuming than reading a 1000 page book. but either way, i think there is a very strong stigma around standard which i think is understandable lol but as long as u can high b5 / low b6 the subject, u have a decent cohort, its essentially comparable to getting a high b5 in english advanced anyway, so ye.
additionally, u say "get a better atar" by staying in advanced... if you're really willing to push yourself, write essays and seek feedback frequently, re-read your texts several times, and genuinely put in the effort in advanced u can succeed, its not like standard will be a "free" subject and it is quite the opposite of that. so just keep that in mind, it really doesn't matter if u pick standard or advanced, ultimately its the mark u recieve that will deterimine if u "get a better atar" regardless of the subject