A network I'm working on has only a web proxy (http, https) to communicate outside (mostly used for cache purposes, not whitelist or blacklist support). This requires lot of configuration to all tools to declare proxy, which is quite heavy and restricting in some cases.
I was wondering if a transparent proxy could easier user life, as the existing web proxy has no real advantages in term of security (advanced users configure VPN to go outside and escape proxy restrictions). The only reason I found so far is for logging access to HTTPS website: CONNECT HTTP command requires the requested URL to connect to a SSL website, which cannot be seen if a transparent proxy is used.
The question is: with security in mind, what is the reasons to keep a web proxy over a transparent proxy ?