Hi there,
Building a platformer now where as you slide across any surfaces, your sphere collider gets smaller. Is this affecting the constant forces I am applying for movement, jumping, air control etc? Also what comparisons would be made between decreasing the mass on the player rather than shrinking collider, or both?
Thanks community 
This is something, you just need to test. Otherwise to be able to help, one need more info about what you want to achieve.
Box2D or 3D??
Changing a collider results in a different inertiaTensor vector.
There are, or there could be a few more things.
For 2D, you explicitly set the mass of the body rather than have the mass calculated from all attached colliders however if you set Rigidbody2D.useAutoMass to true then the mass is calculated from the area of the 2D colliders and its Collider2D.density. This means that if you activate auto-mass then the mass is based partially on the area of the collider i.e. colliders with the same density but different areas will have a different mass. This affects both the center of mass and the rotational inertia as expected.
For 3D, you can use Rigidbody.SetDensity which does a similar thing except it’s a density for all attached colliders.