solid diffs are usually reserved for the rear of the car only. Using a solid diff in the front would destroy the handling characteristics. Front one way diffs are good if you meet the following three qualifiers:
1. You are racing on a VERY large track.
2. You are an expert driver and usually win the A Main.
3. You can drive the track without using the brakes.
One way diffs are good for powering out of wide fast turns, but will hinder the car dramatically on smaller technical tracks.
Because they eliminate front braking, you need to have a perfect driving line, and be a very very good driver, otherwise you will constantly spin out.
Braking is almost eliminated when a front one way is installed, so a smooth driving style and fast corners are required to benefit from its use.