on paper the k7 has alot more features, and the af is almost a fast as a d300 but not, as for fps there about the same the d90 and k7 both have a 11 point af system, but the k7 has a far superior build with Durable and functional body, smaller than any other in its class
The K-7 is built exceptional solid and durable, as its chassis is made of high-rigidity stainless-steel alloy and its housing is made of durable but lightweight magnesium-steel alloy. Thanks to 77 special seals applied to the body, it also features a dustproof, weather- and cold-resistant construction, assuring reliable operation even under harsh conditions and at a temperature as low as -10°C. It also features a newly designed shutter unit providing a top shutter speed of 1/8000 second and the outstanding durability to withstand 100,000 shutter releases. Despite all these features, the K-7 is one of the most compact and functional mid-class models in the market, because PENTAX applied all the experience and expertise in camera downsizing the company has developed from the earliest days of film-format SLR cameras,
also the k7 gas built in image stabilisation, which makes the lenses cheaper and i will say it is very good. ( i feel built in image stabilisation on the body is better than in the lens.)
but i always say go and feel for your self. my money is on the k7,
my k20d i had was almost as weel made as my nikon d300 at half the money and the k20d was more weather sealed to, the only downside to the k20d was the fps and af speed, which has improved on the k7 even more.