It depends what brand of each you are talking about, they both have their economy class, while still providing the luxuary class. It depends on which type of suntek or lumar film they use. I used suntek and medico before. No problems and its alreadii been 2 yrs. Try it out, just make sure they warranty it and your golden. Check out their work before you do it. I have had alot of bad experience with tinters.
Yea no doubt it does keep it cooler, suntek hp is ok, i say go for it and make sure you get the warranty. If they do not offer it, then pay a little more, to get it done in a reputable place. In jersey, you can't legally have anything in the front two windows, but can go pitch black in the rear as long as you have side mirrors. I say if you are thinking about going dark and don't want to get hassled do something like 35% all around. If you want to look cool do 5% but be careful, it sucks at night. Or you can even do 20% which is half way. I say look at samples and make a smart choice.
You can find 3m i think in Union NJ they got it. Tropical tints I think its called. But it is like four times that price. So it depends, remember you have 2 get rid of the front tint for inspection in a few years anyway.