This has been discussed to death in other threads here but the short answer is that it depends on you.
The arcadevga 3000 is easy to set up, almost plug and play, but has limited resolutions.
The stock ati card with crt_emudriver is much harder to set up, but offers many more resolutions.
The best stock ati cards for groovymame are the Radeon x300, x600, or something in the Radeon HD 4xxxx family, assuming you have aPCIe motherboard. For an AGP board, the radeon 9250 is good.
In the end, it all comes down to your tolerance for tinkering, tweaking, and fiddling.