Mysql is larger than wamp
In a WAMP environment, a developer is probably more focused on


Coping PHP/Perl/Python
Configuring Apache to get the WebServer going
Using MySQL to store data, far less concern for the MySQL Utilities and other Bells and Whistles
Getting Windows to coordinate the use of Apache, PHP, and MySQL (If you use IIS instead of Apache, that means the environment is a WIMP).


WAMP/LAMP environments was set up with this mind. MySQL would come with the bare essentials for installing MySQL and storing and backing up data. Such bare essential utilities may include:


mysql : Command-Line Client Program
mysqldump : For taking Textual Backups


MySQL comes with utilities for doing


Replication
Table Repair
Load Testing (such as mysqlslap)
Reporting on Stats
things like these (See all the Major Utilities for MySQL)


If a serious Developer wants to be just as serious at prepping and optimizing the database as a Developer/DBA, then MySQL has everything a DBA could want in that bigger download. Downloading both would be just fine in that instance.