I've personally stuck religiously with Olixar Flexishield for my Nexus 4, then Nexus 5, then OnePlus One, then Nexus 5X and now my OnePlus 5.
In terms of durability, life, size, fit, protection, compatibility, comfort AND PRICE, I truly believe that the Olixar FlexiShield is the best case out of any I have ever seen I will continue to buy these for all future phones as long as they last.
The kind of gel material makes them absorb shock without breaking like a hard case.
They're consistently one of the lowest priced cases on the market.
They always fit very well allowing enough space/fit for accessing controls and plugging in a wide variety of 3.5mm cables and chargers.
They have never broken for me, or worn down. The only thing I would say is that the clear ones can get a tiny bit yellow but this is expected, especially living in London. Also, you can only see this when you take it off the phone.
They never impede screen protectors.
They look great and are one of the slimmest non-hard cases I've ever seen, adding minimal bulk.
All in all, just buy one, if you don't like it, you haven't lost a lot of money - but my bet is that you'll love it.