Speed of Tx to Rx
 

Does this attribute help?? I use a DX 3.0 little older model from spektrum but I see all sorts of advertising for quick transmitting. Just curious if this is a huge deal or not?

NOTHING?? This question is to help with the decision to get new radio equipment and if so which type?

The "quick transmitting time" you're referring to is called latency. The lower the latency time, the quicker the response from Tx to Rx. You will feel more "connected" to your model with a very low latency radio system. But don't ask me about Spektrum systems because I have nothing good to say about them.

it helps, I switched from Spektrum to Sanwa and I feel the car more instantaneously but the servo plays a big role too

worse latency time I had was with a Flysky, the best being a M11X with 451R receiver

Absolutely!!