Honestly speaking C5-03 looks obsolete in front of 500, both have similar pricing while 500 offers far more superior options as compared to C5-03.
Nokia 500 uses same OS that is in Nokia N8 (High End Phone) while C5-03 uses older OS which was in Nokia 5800/5530 which now have become very old, boring and will not come in future Nokia phones...
Nokia 500 got 1 GHz ARM 11 processor as compared to C5-03's 600 MHz ARM 11 processor.
Nokia 500 got Capacitive touch screen like high end devices these days while Nokia C5-03 uses old age Resistive touch screen.
Nokia 500 comes with 2GB Phone Memory as compared to C5-03's 40MB which is a joke :P..
Nokia 500 got 256MB Ram whereas C5-03 got 128MB Ram...
Still you wanna buy C5-03? 