MCU to MCU communication over UART
It depends actually on your requirements what is 'best'.

If (transmission) speed is an issue, there are mainly some things you can do to improve this:


Increase the transmission speed (this depends on the distance of the wires and the noise).
Decrease the start/stop bits (this reduces the certainty the values will arrive ok)
Pack your data (takes more processing time possibly, and more programming work, but can be faster).


About the third option: since you are mostly sending values, you can make some improvements. So you can send them as float (by sending the float data, with the length of sizeof(float)). However, note there could be inaccuracies in the last digit.