Quality is different too BitFenix's standard is kinda high compared to Aerocool

Randylee which chassis you're comparing against??

It's different for everyone but I'd say some chassis are better than others.. I'll look at these things:

Build quality - is the material used solid? is the paint gonna chip?
Practicality - you'd look at airflow mostly unless you're looking to modify it
Size - can I place a 480mm RAD there? will it fit under the table? or could you carry it to a LAN party? it depends on the person really
Style - Does it look nice? or doesn't it matter at all??
Price - Can I afford it?

well... tech issue...it's mainly more towards features rather than tech, such as the availability of front USB3.0 ports, removeable HDD cage, Black interior, windowed side panel, RAD support etc etc...

My advice for a chassis is that you get something you really like and will not get bored to look over a few years