Off the top of my head, DM maps in UT2004 include, of course, DM-Rankin, DM-1on1-Albatross, Deck17, Rajigar, Morpheus3. None of these look feel or play the same. If you gop out of the DM field, you get CTF-MoonDragon, CTF/BR-BridgeOfFaith, or even CTF-1on1-Joust which, like it or not, is one of the most intesting CTF experiment out there.
UT2003 includes such memorable and varied stuff as Oceanic, Gael, Insidious and Leviathan.
I'm not saying the UT2004 exclusive maps are all awesome and varied. I'm not saying the UT2003 maps suck and are all the same. But you know what, UT2003 has a smaller number of maps, and quite a bit of them were just plain not good. I just mentioned Oceanic and Gael I mean Jesus fucking christ, and I say that when I myself have a personal liking for them, but wouldn't defend them against anyone because deep down, I know they suck in both visuals and gameplay. UT2004 might not be absolutely perfect in everyway, but along with all the good and bad UT2003 maps, it has such a truckload of new ones that you are bound to find variety in them, in both visuals and gameplay, and even (gasp) originality. Yes, UT2004 has things like Irondust while UT2003 has Inferno and Tokara, but you can easily find example the other way around. The UT2003 main DM map is Antalus, and I, a great fan of Dave Ewing's work, can't stand how bland it is. Rankin, though I have a deep contempt for it, I admit is more intresting to play, for many reasons.
Yet I still think CTF-Face3 was the best iteration of Face.