‘Compare with’ and ‘compare to’ are often used interchangeably, and neither is likely to seriously mislead a reader. However, there is in fact a difference between that can be useful to keep in mind.
Compare to is best used when the purpose is to draw attention to similarities – most famously, perhaps, ‘Shall I compare thee to a summer’s day?’, or, more prosaically, ‘The results can be compared to those found by other researchers’.
Compared with is useful for drawing attention to both similarities and difference – for example, ‘Our findings reveal considerable variance compared with those of other researchers’.
