Brett

Frontend Features: 
 – adds a toolbar to the bottom of WordPress pages that will show meaningful information that helps developers to create optimized WordPress sites. 
 – Info includes SQL queries, query vars, peak memory usage, and a filetrace.
Backend Features: 
 – Provides a very basic checklist with suggestions for development. 
 – Shows basic server stats and information 
 – phpInfo 
 – WP rewrite rules (coming soon)

Developer Toolbar

Adds easy to access data for developers, including a fixed toolbar to the bottom of pages that shows query data and memory usage among other data.

Takis Bouyouris

<h4>Performance Profiler</h4>
WordPress Performance Profiler plugin silently monitors the resources consumption in the backend and frontend of your WordPress installation in order to provide overall usage and load statistics for optimization and debugging purposes.

Performance Profiler

Performance Profiler plugin silently monitors the resources consumption of your WordPress installation.

Developer Toolbar vs Performance Profiler