There is no PC version of 2K5. 2K5 was developed on the original Xbox and ported over to PlayStation 2. The "PC" that you're referring to is that the editor is a program you can download and install on your "PC".
I'm currently playing on PlayStation 2 and quite honestly, the main differences between Xbox and PS2 are the following -
1) 2K5 easily looks better on Xbox but the PS2 version still looks damn good. Xbox version seems more crisp and clearer at least from what I remember.
2) The Xbox version has custom soundtracks and while I had an idea about this years ago, I couldnt get it to work the way I wanted it to so I scrapped the idea but for those who love this feature, its Xbox all the way.
3) The Xbox version has a patch that eliminates the "clipping/negative yardage penalty" glitch for offensive plays but still remains on special teams plays. I have every penalty maxed out and in three games, have only seen the clipping penalty glitch once and it was on a punt return. As long as its just here and there, its no big deal to me.
4) The Xbox version has a built in hard drive that allows you to see "video" highlights during the halftime and postgame shows. On PS2, its just "photos" unless you're like me and have the PS2 HDD.
5) Transferring roster and/or franchise files to and from your PC is the quickest, easiest and simplest on Xbox. PS2 takes a few extra minutes and requires the PS2 Save Builder program for your PC but I dont mind it.
For FINN's editor, go to -
http://www.nfl2k5rosters.com
You'll see version 4 on the left side which includes the ability to edit PS2 Max Drive files.
I'm in the process of creating a 2010 roster for PS2 that will hopefully be finished after the NFL's final cuts that will include EVERY 2010 drafted rookie, updated rosters, head coaches, ratings and schedules.
If you dont want to wait, you can always download a 2010 roster or franchise file thats already been posted on the above web site.
Hope this helps.