It would be easiest, but not necessarily best, to have the Arduino send a response after every command.
I need to keep latency down so that this will be pretty close to realtime, because with 2 3000w motors on a 25lb contaption, it could get moving pretty fast. I also will be running an if statement with a few mathematical equations thrown in there, because I need to vary the range of differential drive turning depending upon the forward speed so I don't throw tracks or flip the thing 
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Would that method of sending sensor data cause any noticeable slowdown?