Both aircraft have their pros and cons, but there are no major advantages or disadvantages to either; they are both well-designed trainers. As flyfish and J.A.F.O. have said, choose your school on other factors (price, proximity to your home, feedback from other students, etc.). And Maz's suggestion is great.
the thing is so unstable that it's very tiring to fly it for any distance. The stall behaviour (a rapid wing drop followed by an exciting plummet) is not too safe IMHO.
I disagree. Possibly the aircraft that you flew had been in an accident or was otherwise severly out of rig. Anyway, the problems that you describe certainly don't match my experience on type, such as it is (6 hours).