Well since no one has tried to talk you out of it yet, here goes.
I was in almost the same position you are about 2 weeks ago. I had played Madden 2003 on my PC & became engrossed in franchise mode. I got my first xbox right around the time that ESPN 2k5 was about to be released. I picked it up & began my franchise. I loved the way the game played, although there were a few things that I didn't care for about the team management interface (like the amount of effort required to view a player's age). I just finished the Superbowl about 3 weeks ago & moved into my first off-season. Let's just say I was not impressed with the draft or player progression. I tried looking online to see what I was missing & for some help on how to make sense of the mock draft, the rookie report & the scouting combine, but didn't find much help. Being a CAG I wasn't too interested in shelling out for the game guide.
When I saw Madden 04 for $5 new at ebgames.com I figured that since I was so into the franchise mode it would be worth it to switch back to Madden. I picked it up & popped it in the xbox as soon as it arrived.
Now I don't want to start a holy war, because I think there's just a lot of personal preference in which you like better. I also understand that I'm comparing 2k5 to Madden 04, but from most of the reviews I read the biggest difference between 04 & 05 was geared towards the defense. Anyway, I spent a couple nights just familiarizing myself with the slightly different controls, getting a feel for how the game played in practice mode, and setting up my franchise. When I finally jumped into a game, let's just say I was severely disappointed in how the game played. To me it looked & felt much more like a football computer game, when 2K5 looked & felt like the real thing. Again, not trying to upset Madden fans here, just giving my point of view to the OP.
So after playing one game of Madden I'm ready to switch back to 2K5. Maybe I should give it more time, or maybe I should try Madden 05, but I don't have a lot of gaming time as it is. I decided that although I really enjoy the franchise aspect of it, the whole point of assembling a killer team is so you can have a blast destroying the competition with it. I decided I'm willing to overlook the shortcomings in the franchise portion, because the enjoyment of the actual game portion is so much greater (for me) in 2K5.
Good luck in your quest, whatever you decide! Oh, and for what it's worth, I think I actually found the most help in the
"expanded" online manual from the official 2k5 site.