All other things being equal, Lift gets the edge thanks to their huge selection of wings and boards. Flite only offers 2 wings, Lift already has 8.
Lift’s 4’4" board is also ideal for surf riding or any advanced riding in general. The folding propeller gives Lift another edge in surf riding since the prop is a huge source of drag when you’re just trying to glide without power.
I’m not aware of any additional battery safety that Fliteboard has but I have seen their employees constantly spreading misinformation about Lift. That alone should tell you a lot about the type of company they are. The fact that they won’t let you demo the board before buying is another red flag in my opinion.