MyISAM doesn't support transactions and only supports table-level locking, so a heavy concurrent read/write workload will bring it to its knees. Generally you shouldn't use MyISAM anymore unless you know what you're doing and have a specific reason for doing so.

InnoDB is much more crash-safe, supports transactions, and can support concurrent read-writes using row-level locking. It's generally a much more advanced storage engine than MyISAM and it's what Oracle is investing its development efforts in going forward.