Hi!
I'm not doing an SSP units (but I considered doing them), but the best way to compare SSP, advanced and normal courses is to look at the unit of study guides and compare them side by side.
Normal vs Advanced For Life and Evolution, the normal and advanced units cover the same content and have the same assessment. But the advanced program will expand on the content a bit more, and probably go through it at a faster pace since they expect more of you as a higher achieving biology student.
From the BIOL1906 unit guide:
Life and Evolution (Advanced) has the same overall structure as BIOL1006 but material is discussed in greater detail and at a more advanced level.
A small difference is that there is one more field excursion for the advanced program then the normal program.
SSPAs for the SSP Life and Evolution, it's quite different to the other two. It differs in terms of assessment, textbook, practicals (and probably content, to some degree). No factual basis, but I would expect the assessments to probably be harder, because again, they expect even more of you as a biology high achiever.
Other ConsiderationsApart from an academic POV, something to consider is when the classes for each unit are offered. E.g. SSP & Advanced units share lectures, and SSP has set days/times for all of its classes.
Personally I opted not to do any Advanced/SSP units because I didn't want any added difficulty/pressure for uni at the moment. And also because they didn't fit well with the rest of my timetable. But that was just the decision I came to myself. Do consider your own circumstances, the workload of your other units this semester and the logistics of these units in making a decision that works best for you! Remember you have up until census date to change units, so you could always try one and see how it goes!
Hope this helps.