Now that you mention it, I was somewhat curious.  I ran the following simple query on both Super User and Stack Overflow to see how many users had edit permission (>= 2000 reputation):

    SELECT
        COUNT(*)
    FROM
        Users
    WHERE 
        Users.Reputation >= 2000

Which returns 488 for Super User, and 18890 for Stack Overflow.  As a percentage of total users (i.e. commenting out the `WHERE` clause in the above query), and repeating the query for Android SE while we're at it, we get:

    Super User:     (  488 /  136571) x 100% = 0.357%
    Stack Overflow: (18890 / 1582958) x 100% = 1.193%
    Android SE:     (   32 /   19260) x 100% = 0.166%

Given these numbers, it appears as though Super User has roughly 3.3 times *less* editors as a percentage of all users on the site as compared to Stack Overflow.

----

I also thought it would be cool to evaluate the above based on number of questions; so below are two values, the first is total questions + answers divided by users, the second is questions + answers divided by number of users w/ edit permissions:

    Super User:     (151k + 265k) / 136571 ~= 3.1 Posts/User
                    (151k + 265k) /    488 ~= 852 Posts/User w/ Edit Perms

    Stack Overflow: (4.2m + 8m) / 1582958  ~= 7.7 Posts/User
                    (4.2m + 8m) /   18890  ~= 646 Posts/User w/ Edit Perms

    Android SE:     (11k + 16k) / 19260    ~= 1.4 Posts/User 
                    (11k + 16k) /    32    ~= 844 Posts/User w/ Edit Perms

Thus, it looks as though Super User has more posts per user than Android.SE, with a similar number of posts per editors.  However, Super User also has seven times the volume of posts, which is likely a big factor.  Stack Overflow has a significantly higher number of posts per user, but also has a proportionally higher number of editors, obtaining the lowest number of posts per editors.