The 13" 1.7GHz i5 air is about the same score as my 2011 13" 2.3GHz i5 pro :/
That's because Intel is using some very, very, very strange numbers for their GHz ratings. The 1.7 GHz means "this processor can run with two cores at 1.7 GHz forever without damaging the MacBook Air through excessive heat". The 2.3 GHz means "this processor can run with two cores at 2.3 GHz forever without damaging the MacBook Pro through excessive heat".
Both processors are mostly limited in their speed by heat production. For a short time, when the heat doesn't matter, both run at the same, much higher speed. The MBA processor can also run a lot faster if only a single core is used, because that single core can probably run around 2.5 GHz producing the same heat as two cores at 1.7 GHz.
(That's also why the quad core processors have lower numbers. If only two cores are used, they run at a much higher speed, but with four cores in use the speed has to be turned down a bit to reduce the heat. So the "official" GHz number is lower than for a dual core chip).