Much y many no se utilizan en las mismas circunstancias. Much se refiere a cosas incontables, many a cosas contables pero la comparación de much y many es la misma.

Particularidades
comparación de much much - more - most
comparación de many many - more - most
mucho más (referiendose a un conjunto) much more; far more
mucho más (referiendose a determinado elementos) many more; far more
Ejemplos
Nowadays I have more time for my hobbies.
This year, we will have more peaches than last year.
Some plants need much more water than others.
Peter has many more friends at his party than Paul had last year.
* Paul has much more apples in his garden than Peter has.

* En el lenguaje coloquial se usa much more también en relación con sustantivos contables.