Different water temperature in different faucets
Bathtub and shower valves have (and are required to have) anti-scald features which limit the temperature. Depending on the valve that may be somewhat adjustable - check the owners manual for it (look up on the web if you don't have one.)

I believe the reasoning is that a small child or invalid would not be able to get out of the tub, while it's assumed that they could pull their hands away from a sink. It is in response to actual burn incidents.