Gosh...that is such a hard question to answer.
I like having my iPad minimal in terms of case. That lead me to getting a skin for the back and an Apple Smart Cover for the front. I don't think there is a solution that is lighter in weight than this combination. But the skin on the back only protects against scratches, not drops. The Apple Smart Cover alone doesnt' offer any protection for the back, and in a sense, it is very expensive even if you get the non-leather model.
After the skin started peeling off (in well less than a year's time), I got a Bear Motion case from Amazon. 100% Leather. Heavier, but offers a bit more protection...for front and back. Not sure if the iPad is protected in drop, though. But this case gives you a very nice stand in two positions and is, IMO, much better than the stand you get using a Smart Cover. It has a very wide and strudy base, so it is very stable in the vertical position. And, when typing position, the angle is better - IMO - than the angle you get with the Smart Cover. And the case looks very nice and come with a cloth bag to protect if (which I never use).
I also have a Hard Candy case. This thing offers greater protection than either of the cases listed above. And the good news is I can have the iPad in either of those cases and it + case fit inside this Hard Candy case.
So I have at least three cases for my iPad. Actually, I have a couple other ones and a couple snap on cases for the back.
This case things is a very personal choice. I struggle with it...and there is this waiting game you have to play after a new case comes out.
BTW, my $70 Smart Cover has come unglued around the edges. I need to get some glue to fix it. I didn't last a year. YMMV.
Best.
