City, 1. Countryside, 0. The city wins! OK, so if you took the whole of Wordsworth's poetic works, the score would probably run more like: City, 6. Countryside, 250. Few writers, past or present, have expressed their love for rural life quite so much as Wordsworth. Maybe that's why it's somewhat surprising to hear him say that he never felt so calm as he did when standing on London's Westminster Bridge. He seems surprised himself. Maybe the answer to this riddle is that Wordsworth integrated the city into his general vision of the countryside, breaking down the barrier between the two. But we still think he would have been very unhappy if he had been forced to move to London permanently.
The city's freshness is more beautiful than the freshness of the countryside because it runs counter to expectation. The element of surprise accounts for the speaker's enthusiasm.