You can disagree all you want but statistics paint a different picture, moreso in CTF. I have played in hundreds of league matches, tourneys, scrims and pugs between both games, and have looked at pug stats logs. I can tell you what became a mainstay map for each respective game and those which did not last at all. UT3 tdm/ctf was at about half that of UT2003 in terms of staple maps in the competetive scene. And even Shangrila needed modifying (amp in middle) to become more accepted. Coret was a terrible remake and most disliked it.
Just to keep it simple I'm using DM/CTF as examples of maps which didn't get the axe based on pug stats, scrims, league and tourney usage...
UT3 DM: Deck, Shangrila, Sentinel
UT3 CTF: OmicronDawn, Strident
UT2003 DM: Antalus, Compressed, Asbestos
UT2003 CTF: Citadel, Chrome, Maul, Orbital2 (all which carried over to 2k4)
And you still want to be more technical in terms of proportionate, you're not even including the fact 2k3 shipped with more gametypes on its own. If anything it was clearly obvious Epic was more concerned with getting GOW out in time for MS holiday marketing rather than finishing up and polishing UT3, especially with Midway out of $ and not giving 2 shiz about what happened.