Wired Vs Wireless Question

Hello. I'm wondering whether I should have a wired connection or a wireless connection for my PC. My PC is upstairs while the router is downstairs, and I've measured it and the distance is about 16 meters (the Ethernet wire would be going along the walls, not through them). But I've heard that the longer the Ethernet wire is, the lower the speed will be.
This is the wireless network card: http://www.ebuyer.com/166269-cisco [...] wmp600n-eu

I have an N+N Router and use a cable connection.

Could anyone tell me which would be better in terms of speed?
And if it's the cabling, are there Ethernet cables that are better than ones? I've found out that Cat6 is better than Cat5 but I was wondering if there was anything else.
Also, anything else I should know before making a choice?
Thanks in advance.

The question of wired v. wireless really depends on how much bandwidth you need (like if you are streaming video, you need a lot) and the convenience of placing the cable for wired. Wired gigabit with CAT 5e will always be "faster" than wireless, but the difference may not be important for your application. Wireless, while less hassle, is also susceptible to interference from other devices in the house (microwaves, wireless telephones, etc.) while wired Ethernet is much less so.

No, the distance for wired does not change the speed as long as it is within specifications (less than 100 meters). CAT 6 is NOT better than CAT 5e for gigabit (1000BASE-T) or 100 megabit (100BASE-T) Ethernet. If you use cable, use CAT 5e. CAT 6 or higher is only needed if you are planning a 10 gigabit network, which is not anywhere near a consumer product yet or in the next few years. CAT 6 requires proper grounding at all junctions and all attached devices would have to support the 10GBASE-T standard to provide the 10 gigabit speeds.

Wireless speed will depend on distance and intervening material of walls, floors, etc., and while perhaps more convenient will not consistently deliver the same speed as an Ethernet cable. It may be quite sufficient though if the distance is reasonable.

An alternative is to run a cable and at the end of it attach another router configured as a wireless access point if your wireless does not cover the area well and you want to have multiple wireless devices that can connect in several areas.

That is excellent and will support gigabit as long as all of your routers, network cards, and other hardware do.