The first sentence puts the word "Yan 'an" at the forefront, which plays an important role and highlights the eagerness of "I" to pursue the spirit of Yan 'an. The last two sentences can't achieve such an expression effect. Moreover, the degree of feelings is different, and the first one is stronger, showing the loftiness of Yan' an as an ideal. And Yan' an, I pursue you and show my passion; I pursue you, Yan' an, and show my love; Pursue you, Yan 'an, and show your heroic feelings.
I hope it helps you ~