Unrestricted term limits can easily turn into a system of dictatorship, especially in a system where the president plays a pivotal role in national policy-making.
It's easier for an incumbent to manipulate the political atmosphere to his favor and practically manufacture consent for him and his policies. The possibility for indefinite re-election can also keep authentic opposition at bay when fear of loosing and consequential retaliation is perceived as a real possibility amongst the opposition at election time.
Term limits, on the other hand, is not without problems either: For example, just look a the Bush administration's last-minute push for changes in environmental policies (or the Endangered Species Act) before leaving office. He's not the first president to engage in that kind of departure, but it's a disgusting habit nonetheless.
I still think term limits is a better choice, also for Venezuela. Cháves stepping down does not automatically mean that no one else would be capable of running according to a similar political platform, if that is what the people really want. In a way, it could actually elevate and diversify political participation on the grass-root level in the longer run.