msfvenom is a combination of Msfpayload and Msfencode, putting both of these tools into a single Framework instance. Note: msfvenom has replaced both msfpayload and msfencode as of June 8th, 2015.
The advantages of msfvenom are:
- One single tool
- Standardized command line options
- Increased speed
More information:
https://www.offensive-security.com/metasploit-unleashed/msfvenom/