For a basic set up I would get a Voodoo3.
The Radeon 9200 is a nice card, but its better suited to PPC software.
The extra memory of the Radeon is not really that useful.
I don't know what you mean that the Radeon 9200 is better suited to PPC software? The Radeon 9200 works fine with 68k machines. The Radeon also runs much cooler than a Voodoo 3 which might be a concern for an A4000 desktop. I agree that the extra memory of the Radeon is pretty much useless.
The main benefit of a Voodoo 3 over Radeon is that it has Warp3D support, though it might be argued that is too slow on 68k to be of much use.
The benefits of a Radeon over Voodoo 3 is lower temperature output and DVI support. And DVI support is nice if you want to use HDMI as only a simple adapter is required. Also cost; a Radeon 9200 you should be able to find around $20, a Voodoo 3 lately can be anywhere from $50-100. Though if you have to buy 2-3 Radeons before you find one that is 5V only you didn't save anything.