Greece would swap one set of problems for another set of roughly comparable problems. I would say neither option is significantly better or significantly worse, but only if you look at Greece in isolation.
If, however, you include the broad Eurozone and world economy, it's no-contest. Greek default and exit from Eurozone would significantly hammer the latter, and effects would be felt throughout the world.
It should be painfully obvious that Greece stands a better chance of a recovery if they don't trigger another major recession and financial crisis and alienate their core customers for good measure. It's also entirely possible that Greece would destabilize as a result, with even their democracy being threatened. This is only a possibility, not a certain result, as other effects I mentioned are.
As I said earlier, they want to avoid austerity, but it's only a question of how it will come by. It may be through spending cuts or it may be through hyperinflation. Those are choices they have right now.
McHrozni