My first 'decent' guitar had a soft case, because I couldn't afford a hard one. The back of the guitar was split open in a relatively minor accident. Never again! I've also seen headstocks and necks suffer the same fate...

My preferred case is the Hiscox (UK made) which is an ABS plastic moulding strengthened with some sort of foam resin, and finished with padding. It will take my weight (17 stone) jumping onto it - that's good enough for me (and my guitar!). It has also taken tumbles down staircases ('helpful' souls after gigs!), and my 30 year old Yamaha is still as good as new!

There are other cases which look similar, and are just as light, but can't handle the aggro!!