Flavorizer bars also do a better job of heat distribution than briquetts/lava rock, That means more even heat across the grill instead of hot and cold spots. This is also affected by the design of the burners and their number.
FWIW...I never bother to clean my Weber's flavorizer bars. They are right on the flame, and get much hotter than the grate. Every time I heat my grill, everything on them from the previous cook is quickly reduced to ash, so no cleaning is needed. I've been using my current grill very frequently for 3 years now, and have never had any problem caused by dirty flavorizer bars.
If you don't like the food, have more wine