Difference between 102 and 122

What is the basic differents between movement type 102 and 122.

1.Both of transaction code are used for reversal of GRN.

2.In both of the transaction same accounting key are generated as WRX (Dr.) and KBS (Cr.)

I have seen only one differece in these mvt. as If you are using MIGO with 102 (Cancel option) then all the qty of the GR will be reversed, you can not reverse the partial qty of the GR.

but if you use 122(Return Delivery option) then you can also reverse the partial qty of the GR.

So any one can suggest me, what's the business senarios by which we can differenciate bw both mvt. and take the decission for selecting one of them.