I have a Lithium 12 and 9 and like them both. Smooth power, good turning, easy relaunch and great bottom end grunt. You can adjust the bridle and leading edge attachments between low/medium/high bar pressure settings. I am using mine on low and its all good. They are low weight too - which helps the flying characteristics. They are good for beginner too.
I haven't used Slingshots so I can't comment on them, other than that they also have a good reputation.
However, if you get two second hand kites (as per previous posts) then you won't worry so much about crashing (and possibly trashing) them. My first kite spent a lot of time hitting the water, and sometimes washed in on rocks.
9m review:
kitesurfing-handbook.peterskiteboarding.com/reviews/2013-airush-lithium-9m12m review:
kitesurfing-handbook.peterskiteboarding.com/reviews/2013-airush-lithium