[Rosalind Franklin]

Why does phenanthrene behave more like an alkene than anthracene?

I drew the contributing structures and phenanthrene had more structures than anthracene but how does that help in understanding double bond character? Does it behave more like an alkene because the bonds are shorter than in anthracene or normal benzene? Due to more resonance?

I also read something about resonance energy being different for phenanthrene and anthracene but could not understand the explanation properly. How is resonance energy useful here?