Both LD3 and CD3 come in pro kits. Are you buying in the States or elsewhere? I bought my kit from Hong Kong.
I love my LD3. I race against a MTX3, Serpent 710, 2 V1 RR's and the car is able to keep up. Sometimes I'm not good enough to keep up but the car is. I would go for the CD3. I have only heard good things about it.
There are a lot of good cars out there. Spare part availability is the biggest concern.