Try the free one first. See if you like how it works. If you don't like it or can't get it working, try something else.
That may sound obvious or trivial, but since they're all capable of virtualizing Linux, it's going to be other factors that ultimately influence your decision (such as price or ease of use). Since we don't know which factors you value most, nor what level of experience you have, you'll have to make the choice yourself, based on the factors you value.
Either that or you have to post a prioritized list of all the factors you value, assigning each a weight or cost, and describe your level of experience in installing non-trivial software like virtualizers and Linux systems.