I was debating over the same thing last week and I ended up buying a Gf3 Ti200 and I'm very happy with it. From what I was told and from the reviews I read the GF4MX440 does not have full Direct X 8.1 support (the MX440 wont take adavntage of DirectX 8.1 in future games) Perfromance is right between a GF2 and a GF3 so it will be about 10-15% slower than a Ti 200 stock.
Also the Ti200 cards all seem to be very overclockable. My 3D Mark 2001 score went up over 1000 points after overclocking my card.
I have an aging GF2 MX card as well and after reading the article linked on the frontpage (to xbit), I went out and ordered a GF3 Ti200. I'd been planning on getting that videocard for my new rig soon and the news that nVidia has sold out of the Ti500 chips and is close to selling out of the Ti200 chips encouraged me to buy. I also looked at MX440 cards and after seeing the reviews I was pretty much sold on the Ti200. The added performance at stock speed, coupled with similar price ranges and the high overclockability of the Ti200 (up to Ti500 levels usually) outweighed any benefits that the MX440 had.
So if you're looking for advice, I'd say do what I did and get a Ti200 card (mine is an Abit Siluro Ti200 w/ TV Out, I got it for $138 from SR Systems)