the bias of choosing the action which is easiest

Laziness.

"I'm not lazy, I have a least-effort bias!"

Thinking, Fast and Slow by Kahneman

A general “law of least effort” applies to cognitive as well as physical exertion. The law asserts that if there are several ways of achieving the same goal, people will eventually gravitate to the least demanding course of action. In the economy of action, effort is a cost, and the acquisition of skill is driven by the balance of benefits and costs. Laziness is built deep into our nature.

http://en.wikipedia.org/wiki/Principle_of_least_effort

The principle of least effort is a broad theory that covers diverse fields from evolutionary biology to webpage design. It postulates that animals, people, even well designed machines will naturally choose the path of least resistance or "effort". It is closely related to many other similar principles: see Principle of least action or other articles listed below. This is perhaps best known or at least documented among researchers in the field of library and information science. Their principle states that an information seeking client will tend to use the most convenient search method, in the least exacting mode available. Information seeking behavior stops as soon as minimally acceptable results are found. This theory holds true regardless of the user's proficiency as a searcher, or their level of subject expertise. Also this theory takes into account the user’s previous information seeking experience. The user will use the tools that are most familiar and easy to use that find results. The principle of least effort is known as a “deterministic description of human behavior.”[1] The principle of least effort applies not only in the library context, but also to any information seeking activity. For example, one might consult a generalist co-worker down the hall rather than a specialist in another building, so long as the generalist's answers were within the threshold of acceptability.

Generally "bias" implies that you're talking more about beliefs than an actions.

If think one thing and do another because it's easier, that's referred to as "akrasia" around here.

If you're saying you believe the easier action is better, but then believe something else after putting more thought/effort/research into it, that does fall into the bias category. I don't think that's exactly cognitive laziness, more action-laziness affecting cognition. I don't have a good name, but it's some sort of causal fallacy, where the outcome (chosen action) is determining the belief (reason for choice) rather than the reverse.

Laziness can sometimes be a form of decision paralysis - when you're facing a new and difficult problem and not sure how to approach it, your brain sometimes freaks out and goes to default behavior, which is to do nothing. That's why it's important to make plans and pre-commitments.