This video will give you the key differences between the Honeywell LYNX Touch L5100 and L5200 wireless security systems. Right off the bat, you can tell the L5200 aesthetically is much different it only has two solid push buttons while the L5100 has four. The shell of the L5100 system has a grey contrast while the L5200 solid white. The L5100 which is the older panel will only allow you to input 16 user codes while the L5200 system can handle up to 32 user codes which are perfect for business security. As a correction to this video the L5200 panel can only handle 64 wireless security sensors, not 80. The coolest upgrade for the L5200 is that the end user can view a camera from the actual 4.7-inch touchscreen display. 

Update - Both of these DIY security systems are no longer in production they have been replaced by the Honeywell LYNX Touch L5210 wireless security system the link will be provided below.

Alarm Monitoring:
Geoarm Security Blog:
Honeywell L5210: