If I recall correctly, 3D acceleration cuts down on some of the jaggies in the world's polygons, but as others noted it uses worse textures than software mode. If you have to pick one or the other, software mode is better.
That said, there is a tool floating around (MMResTool) that allows you to force D3D Mode to use the textures from Software Mode. Here's a link:
http://www.celestialheavens.com/forums/viewtopic.php?t=9873&highlight=
What's not clear is this comment from GrayFace: "My patch uses hi-res textures by default since version 1.4" (
http://www.celestialheavens.com/forums/viewtopic.php?t=11668&highlight=texture).
So, potentially, if you have GrayFace's patch installed you can use D3D Mode with the higher res textures from Software Mode. But if I'm interpreting GrayFace's comments incorrectly, then you could try using the other tool (MMResTool).
Of course, it sounds like you still need to get 3D acceleration working in the first place. I wish I could help, but I don't have any suggestions that others haven't already made.