Translation:Why do you always compare yourself to Sofia?
Like the sentence "People often compared youth to Spring"?
It's aslo with "kun"; "oni ofte komparis la junecon kun printempo". (the same source)
Thanks for making me pay attention to the difference between "compare to" and "compare with" in English. But in Esperanto, both are "kompari kun", as it seems to me.
The entire page of "kompari" in Plena Ilustrita Vortaro de Esperanto is about comparing with. Only the third definition of "kompari" is "Rilatigi tion, pri kio oni parolas, kun io analoga, por fari la ideon pli impresanta, pli drasta aŭ pli poezia" with only two Esperanto examples, which use "kun" (I just translated one of them). So, I think this meaning is not so common in Esperanto generally, but it's expressed with "kun", not "al" as in English.
I tried random Google search of "kompari kun" and "kompari al", it turns out "kun" does have a significantly higher popularity (regardless of the nuance in definition) than "al", in fact the use of "al" is very rare. I am convinced for now. Again thanks for your sources and time.