I've never used the 300 f/4; but it is far superior, sharper and a lot faster to focus, lens. Also, it can happily take the 1.4 tele-converter; and even with the 1.7 tele. it still maintains sharpness.
The only downside, when compared to the 70-300VR, is the lack of VR .. so, you will need to learn how to hand-hold it and watch your shutter speed.
In all fairness, I don't think it is a fair comparison ( 300 f/4 vs. 70-300VR). They are two very different bits of kit.