Difference between Layer 4 and Layer 7 VIP ?

Biggest advantage of a layer 7 VIP, standard with a HTTP profile as the example, is the ability to both manipulate data inside the payload such as headers, cookies, content, etc.. as well as make decision on that content. The biggest advantage of Layer 4 VIPs is the ability to make decisions just on the packet basis and can be offloaded into specialty hardware bypassing the CPU for most of the conversation, a PVA chip.