The 5200 isn't up to the speed with the GeForce3, as it was designed to be a replacement to the aging GeForce4 MX. The one benefit which comes to mind is its support for DirectX 9 features, and its compliancy. Plus, many GeForce3s didn't feature TwinView support.
Furthermore, a comparison:
GeForce3:
- DirectX 8.0 and OpenGL 1.2 compliant
- Pixel Shaders 1.1 and Vertex Shaders 1.1 support
- 4 rendering pipelines, each with 2 texturing units
- 6.4 GB/sec. bandwidth (Ti 200), 7.36 GB/sec. (original), 8.0 GB/sec. (Ti 500)
FX 5200:
- DirectX 9.0 and OpenGL 1.3 compliant
- Pixel Shaders 2.0 and Vertex Shaders 2.0 support
- 4 rendering pipelines, each with 1 texturing unit
- 6.4 GB/sec. (non-Ultra), 10.4 GB/sec. (Ultra version)
For a full comparison, you can use the tool here:
http://www.area3d.net/compare.php