A is as good as if not better than B
Solution 1:
That sentence always means "A is at least as good as B". (I guess in your scheme you'd represent that as A≥B, assuming that "more" is "better".)
The reason for this is that "if not X" means roughly "or maybe even X". For example, "many if not most people like summer better" means "many people, maybe even most people, like summer better". So your sentence can be rephrased as:
A is as good as — maybe even better than — B.