Nikon has huge range of lenses and accessories, original and third-party. They also have a huge user-base, which means it'll be a lot easier to buy/sell/trade your system, either in whole or in parts. And for some strange reason, whenever you hold a Nikon, laypeople tend to think you very pro. It's the brand name, lah. (I've heard of people comment, "That pro use Minolta only. Like that very good, meh?")
KM, in my (probably biased) opinion, is technologically more advanced than Nikon. Case-in-point, the anti-shake system. Once you use it, I swear you'll never want to use another system without it. Other brands may have VR lenses, but if I may jump the gun and make assumptions, the fact that you're considering a D50 probably means you won't be able to afford the VR lenses. And even if you do buy one, it's just one lens, and might not be the lens that you'd be using most of the time. KM's D5D effectively converts ALL your lenses into VR ones!