Mainframe and Client/Server Environments

 
Respond to the following in a minimum of 175 words: 
Consider the following scenario: 
Your manufacturing company has operated with a mainframe IBM computer for more than 20 years. Recent technological advances have brought opportunities to replace that mainframe-based computing environment with a client/server environment. You have been tasked with responding to senior management about the security issues involved with replacing the existing mainframe computer environment with a client/server platform.
The salespeople you deal with from each vendor believe the current mainframe environment costs about $500K a year to maintain from a security standpoint, while a client/server environment would cost about $325K a year. But cost is not the only consideration. No PII or SPII data is contained in this manufacturing platform. It is strictly a final product for sale application. 
Outline and review a typical mainframe enterprise security footprint. Do the same for a possible client/server environment. This could include the use of the cloud for distributed computing, but that would also include unique security concerns. 
Discuss the following: 

Based on your outline, which of these environments is more secure and why? 
Does your outline show commonalities that could permit both the mainframe and the client/server environment to coexist from an enterprise security perspective? If so, what are they?