Hello,
The NH-D14 is indeed a very good cpu cooler. BUT it's freaking HUGE !!
However, you must remember that most reviews of the D14 are made on an open test bench.
When the review uses the D14 inside a case, it comes very close to the H70, with a difference of 2-3°C.
Also, the H70 is much more prettier inside a case. The D14 is beige and brown, with a BIG metal heatsink. The H70 is all black with a black radiator and all.
Furthermore, the D14 will block some memory slots. That means you can't have tall memory heatsink.
It might also not be compatible with your case/motherboard :
http://www.noctua.at/main.php?show=compatibility_gen&products_id=34&lng=en
All in all, I'd go with the H70. It does not perform as well as the NH-D14, but it's close, and the inside of your case won't look as if it's been filled with a big piece of metal :
Noctua NH-D14 :
http://img39.imageshack.us/img39/1549/dscf1304resize.jpg
Corsair H70 : http://img690.imageshack.us/i/img0001gn.jpg/
In the pictures above, both are inside a Cooler Master HAF 922, which is a big mid-tower case. Most are a little bit smaller.
I hope this helped,
al360ex