Both have the same number of pipelines, but the X700P's core is clocked slightly higher. The 9800P has double the memory bus width, while the X700P has slightly faster memory. It'd be pretty close, with the 9800P maybe winning AA+AF benchmarks by a bit, but I'd recommend the X700 for its lower power draw and SM2b capabilities.
There're a ton of X700P PCIe vs. 9800P AGP benchmarks
here, but the two cards use different platforms and CPUs, so just use this as a very general guide.
There's a recent article
here that compares a mere X700 AGP to a 9800P on the same system, and the X700 comes out looking pretty good. Most games tested are pretty old, but I'd recommend a X700P based on these benchmarks. More reviews of another X700 AGP listed
here. You can check if any include a 9800P for comparison. That HIS X700 looks interesting for its Silencer cooler.
But $200 for a X700P seems like way too much, especially if you won't game with it. The 256MB is probably worthless outside of gaming, too. Look for a cheaper card, maybe a 128MB non-Pro.
If you already have it and are happy with it, then stick with it, as it compares pretty well with a 9800P and should draw less power at the desktop. But I'd almost recommend spending, say,
an extra ~$30 for this X800, which should be much faster than the X700P with games (same core and mem clocks, but 12 pipes and a 256bit memory bus). Sure, you may not use it, but it'll have a higher resale value when you want to upgrade down the road. No idea if power draw increases, though it's easy enough to find a PCIe X800 review to compare power draw with a X700P (I'd try TechReport's).
Edit: Actually, forget that Abit. Look for the $240 Asus at NewEgg. It's clocked far higher (475/900 vs. 392/700), uses better components (nicer capacitors and a bigger HSF), has that internal VIVO connector as a bonus, and is a shorter card. All that for $10 more than the Abit. Still pricey for VIVO work, but a far better value than that C3D X700P.