这两个词组的意思基本是一样的，区别在于分别用在可数（many）和不可数（much）的情况下。
请看下面的例句。头两个例子里，people和candy都是可数的名词，所以必须用“as many as”。第三个例子里，time是不可数名词，所以只能用“as much as”。
1. I went to a big party last night. There were as many as eighty people.
昨天晚上我去参加了一个聚会。有多达八十人在那儿。

2。 Please take as many candies as you want as I have plenty.
我有好多糖呢，尽管拿。

3. You don't have to rush. Take as much time as you want.
你不用太赶了。你想用多少时间，就用多少。


as much as+数词时:
这只小鹦鹉可以长到巨大的尺寸,长到三尺长.

This little parrot will grow to huge size, as much as three feet.
（这里的"three feet"强调的是量的概念，所以用as much as。）

as many as+量词:
我们学校今年来了许多外国学生大约有一百来人.

There were as many as one hundred foreign students visiting our school today.
Or:
As many as one hundred foreign students visited our school today.
（这里强调的是具体的数量，所以用的as many as。）

(Sorry. I don't check this web site often.)