Modelling priority/importance in a digital circuit
I understand you want to find out which of the two numbers is larger? You can do that by comparing the bits of A and B, starting at the highest ones, let's call those A3 and B3. 

There are three cases: they are equal, or otherwise A3 is 1 (and B3 is 0), or B3 is 1 (and A3 is zero). In the first case (equal), which one is larger is determined by the next (lower) bit. If they are not equal, take the A3 bit and it tells you whether A is larger. So for the left most bit:

A_is_larger = ( ( A3 == B3 ) * ( input from lower bits ) ) + ( ( A3 != B3 ) * A3 ).

For the rightmost bit the you can simplify this to A1 (assuming that for equal values you don't care what the outcome is).