There is no comparison.

The spore drive is, for all intents and purposes, instantaneous travel to any part of the galaxy.

I think there is a reference to 1.3 seconds to the Beta Quadrant but this might include power-up time but, apparently, distance is not factor and if that is the case then there is no velocity equation that can be used to compare.

The Discovery it would appear (since we are only early in the series at the time of writing) has "normal" warp engines to get where it's going but has the experimental spore drive in development in the hopes of a significant miltary advantage.

Akiva Goldsman (EP) had this to say..

We are not the Kelvin timeline…which is a reboot of the original timeline…We are not part of that timeline, we are the original timeline with the TV shows and the movies that fit into that. We are ten years before The Original Series…Where Constitution Class ships are in comparison to where this Discovery prototype – well one of two prototypes, well now one of one prototypes – are technologically is obviously a variant. We are wildly aware of everything that appears to be a deviation from canon. We will will close out each of those issues before we arrive at the 10 year period and hit TOS.

^Source

Episode 2 of Season 2 has the answer.
A distance of ~51 000 light years would take 150 years using warp drive, while spore drive is instant like in a blink of an eye.

Spore drive doesn't traverse space in the classical Newtonian sense. Spore drive displaces matter into a fibrous network which permeates a dimension allowing swifter transit. Since time is meaningless in the mycelial network.... However the USS Glenn achieved moving 90 lightyears in 1.3 seconds Captain Pike authorized the use of the drive to travel 51,000+light years to the planet Terralysium but time spent was not illustrated. the jump appears instantaneous or least few seconds time delay. Its not a matter of speed but calculating destination.