If you want a pathway to medicine, it is better to do medical science or pharmacy as it gives you a more health-related background. Medical science is the most straightforward option.
No Adv Sci is a pretty common pathway for med. Pharmacy you'll end with a much more narrow study than med sci and more so than adv sci/sci (not that narrow is bad if you really like Pharmacy).
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For OP, as a current USYD student in this area.
Adv Sci seems really ramped up from what you see on brochures, but I will tell you that opportunity is always there for those that take it in the Science Faculty.
A) Even if you don't do Advanced Science, you can still pick Adv/SSP subjects if you have the appropriate HSC marks in pre cursors or good university marks. This also means with a D average and fulfilling the degree resolutions you can also transfer into Adv Sci from normal science upon entry.
B) Adv Sci isn't the hallmark to a better job or anything. If you actually want to work in Science, getting Honours and what you get in that (i.e First Class) is more important. Also employers look at your transcript so if you have good marks in Sci, good marks in units relevant, maybe even taking some Adv units from normal you're in good stead. Plus getting involved in the awesome SciFac opportunities and general uni events and good interview skills
Also racking up research volunteering, summer research scholarships, field schools etc. The work is never done from just getting a high ATAR to get into the course on arrival
C) There are some cosmetic differences between the rules of Adv Sci and Sci. If you get the ATAR for Adv Sci do it-because if you ever want to break one of these resolutions it's like a one page form to drop to normal Science-and getting entry to Adv Sci once in uni is harder imho than getting straight in from highschool.
The first of these is that you have to complete an Adv major. Not every major can be offered at an Adv level so this may annoy you if that is the case (although you can always double science major).
Second rule of Adv Sci is that you can only do 48cp jnr (first year) subs in Adv Sci opposed to 60cp of Jnr. Now on the outset from highschool you may think well that's logical. You may find in uni if you want to change majors you may need to go back and do some more pre-req jnr science units or alternatively release yourself from being pigeon-holed to doing Science only from first year subject choices and want to do some first year arts units or something to have senior arts electives in third year (for example).
Third rule is there are minimum requirements on number of Adv units to get the Adv testamur. 12cp of Int and 24cp of Snr.
Basically don't fret on it to much as it's something cosmetic, aim for the ATAR for Adv to be eligible for USYD scholarships and start there as there's absolutely no obligation to take Adv units in first year. I can tell you of all the great virtues of the Science faculty at USYD, I've been very lucky to have some great professors and go on funded overseas field tours for my major. I've also gotten involved in the faculty from first year student orientation, SciSoc and going to some cool guest lectures. There's so many things I've discovered I didn't even think of coming from HS, go USYD science <3