Renting cameras to test before purchase?
If you mean wide angle lens for landscapes, I don't have much experience outside of the Panasonic 14 f/2.5. It's small, sharp, and hard to beat for the price. I'd probably get a hood for it before any "serious" landscape use.
I think you could get good landscape shots from any lens if you took some time and put some thought into it.
Not a prime but I highly recommend the Panasonic 7-14mm for landscapes. There's a bit of chromo on the OMD but it's not too hard to fix in post.
That lovely lens is a bit out of my price range at the moment considering I just bought the OMD + 2 3 lenses. This is one I'd consider renting or perhaps the 9-18.