to compare to is to point out or imply resemblances between objects regarded as essentially of a different order;
to compare with is mainly to point out differences between objects regarded as essentially of the same order.
Thus, life has been compared to a pilgrimage, to a drama, to a battle; Congress may be compared with the British Parliament. Paris has been compared to ancient Athens; it may be compared with modern London.
Although I was taught to use ‘compare with’ when making routine comparisons – of similar things and for last year’s figures for examples.
Anyone else have any input on this?