Depends on what "night photography" you do. If it's landscapes, you'll want LOW iso and a tripod.Welcome abroad...
If I have the D90, I the first thing I want to do is night photography on its high iSOs. The High ISO performance (ISO1600, 3200, 6400) on your DSLR is very good. The D90 is definitely a good choice if I'm buying a Nikon.