Yes, they can both be installed on the same system - I have both on my Windows 7 laptop and either works fine. I routinely connect to multiple remote networks (one at a time) using one or the other, depending on what type of remote access VPN is available.
Depending on the VPN configurations, you can sometimes even have the two separate clients running and connected. That's not a supported situaiton but it is possible. I can vouch that I've done it.