Your weight is relevant to choose soft, medium of hard flex pattern.
Also your taste and physical condition.
If FIS size is not a must for your exams, choose a female model. Shorter and softer.
I´d go for a soft one. My weight 70kg my height 174cm. Male by the way... XD
About SL skis. Just remember one thing.
They are massively easy to begin a turn with and therefore they do not teach much.
Depending on your physical condition, skills and style, some of them may have a lot of rebound when pushed hard.
Keep this in mind.
Skiing GS skis gives you a different perspective and you need to make them work to turn.
Specially 27m r ones.
If you are not used to ski long skis or GS-like (fake ones) I recommend you to start with ladies 23m soft.
For SL turns I use a Nava Ski with Vist plate FIS standards. Handmade, etc, etc
Great piece. Very similar to the Vist Super Front Tre.
I´ve never used a better SL than those two.
Just look for a FIS ski, try to have some runs with it before buying, and compare brands. Do not pick the first one you see.
For GS I need to change my "old" Vist GS. 180cm long old FIS standards 21m radius. Also Vist plate and bindings.
I´ve been told the 191cm model was even easier to ski with. It was named Super Front One.
Unfortunately they are not producing FIS standard skis anymore to the public. Only SL models accomplish standards.
As I said before look for a FIS rules ski. Try different brands, models and choose which one is best for you.
Good luck in your search.