It can be, it depends on what we’re comparing it to. But, I think the question needs to be a bit more refined.
The question I’d actually be asking is - Can the device support the data rate you need?
Just getting the data back from the sensor is the first number I would consider to answer this question.
For a quick example, assume that you want new data every 20ms (ie, 50 times per second), and the data is 32 bits long. You therefore need a datalink with at least a rate of 32 * 50 bits per second, or at 1.6 kbps link.
You should re-run this calculation with your numbers, and see whether I2C or RS232 can meet your requirements.
Some additional constraints you might have:
If you have to have your software “block” while the sensor transmits the data, you have a new timing constraint to consider. You may also be able to collect the data “asynchronously” in the background to help meet this constraint.
Additionally, the transmission time will (likely) be the biggest delay between when the sensor makes an observation, and when that observation is available for use in your controls code. How much this matters will depend on how you are using the data to control the robot.