How to configure iptables MASQUERADE rule for set of secondary IP address?

Issue

• I have RHEL with iptables as a firewall. I have set of 3 public IP address for WAN.

eth0   1.1.1.1  # 1st IP address
eth0:0 1.1.1.2  # 2nd IP address
eth0:1 1.1.1.3  # 3rd IP address

eth1   2.2.2.2 # LAN segment

• I added MASQUERADE rule to allow Internet access from my LAN as below:

iptables -t nat -A POSTROUTING -s 2.2.2.2 -o eth0 -j MASQUERADE

• Now outgoing connections from my LAN to WAN will be masquerading with 1.1.1.1 public IP. How can I change masquerading ip "1.1.1.1" for any other as e.g 1.1.1.2 or 1.1.1.3 ?
• How to configure iptables MASQUERADE rule for set of secondary IP address?
• What is the advantage of using iptables MASQUERADE target over SNAT target?