Do different brands of cell phone (LG,Samsung,Nokia,Motorola) get better service than others?

I have heard that nokia and motorola get the best service via cingular and that samsung gets the worst...I would have to say that I agree because I used to have a Razr and now I have a blackjack and it gets much worse service. I was just wondering if anyone had any input as to whether this is semi-true or not.