The 305 has more features than the 30. Most important one is a manual ground balance. I wouldn't mind testing a 305 myself, but I think it has a slow response time and I don't like that. Steve.
I have the X30, and would love to have had the 305 instead, however a year ago it wasn't around. The extra features make the 305 more like the old X-Terra 50, but much cheaper.