Do you mean you intend to network the PCs together just to share files or network them via a router to share internet access?
If the latter, then a wireless router will give more flexibility in the future when you need to add another PC or a laptop ('cos you will) :D
I use 2 'homeplug' devices to connect my son's Playstation PS2 and the PC in his room to the router downstairs. They were literally plug and play and required no setting up at all.
So, in my case I use a wired connection for the PC downstairs, wireless for the 2 laptops and homeplug for the kit upstairs.
The wireless signal would have been fine in the boy's room but it was easier/cheaper to connect the PS2 this way.
If you add up the cost of wireless cards for your 2 PCs against the cost of the homeplug units it may help in your decision. Of course the homeplug don't suffer with signal 'drop out' if you have a large home or one with thick walls.
Hope that helps.