[mdasen]

It isn't about better vs worse. It's about the right tool for a job.

For example, if you needed to store key => value pairs, how would you do that? If you use an array (array[0] = ('key', value')), you would have to iterate over the entire array to find the key you're looking for (Order n), but if you use a hash table, you can do key look-ups in constant time (Order 1).

MySQL's different storage engines provide similar opportunities to use different ways of storing data for different ends. MyISAM has amazingly fast read speeds, but is really poor under write conditions. Sounds like a crappy storage engine, right? Well, what if you have a table of zip codes and their geo-coordinates? How often are you going to be writing new data to that table? Every couple months in a batch update? So, if you put your postal codes in a MyISAM table you can take advantage of high read rates and ignore the fact that MyISAM is terrible for writes since you don't really write to the table.