No, it's not like an MX version. It's more like a Geforce 2 GTS compared to a Geforce 2 Pro...
They're both the EXACT same card hardware-wise, but simply have different core and memory speeds. Here they are in oreder of performance:
GF3 Ti500 (240core/500memory)
GF3 (200core/460memory)
GF3 Ti200 (175core/400memory)
I think the Ti200 is an excellent deal. In most cases you'll be able to overclock it to regular GF3 speeds, and it costs a lot less.