The answer to this question depends heavily on the business goals, as well as the client.
If you are doing business with an enterprise level client who is well established in the marketplace, they are less flexible and cannot adapt to changes as quickly. Therefore, stability is an absolute requirement in most cases. There are exceptions for research and development and entering new verticals. Faster finishes first in some cases.
These types of clients generally understand that good software takes time to develop, and will work with you to try and meet the goals.
For a new startup, the rules are drastically different. As a startup, you need to know right away if the product that you are building will indeed fulfill a need as your marketing research predicted. For a startup, getting a prototype out in the market as fast as possible can garner lots of valuable feedback about the direction the product should go.
It can also establish you as the market leader, helping you gain valuable market share in a new vertical before it becomes saturated with competition.
Since startups are small, flexible, and can rapidly adapt to change, this model works out best for them.
In summary, there are other factors to consider, but the main idea is that every project is different and will have different quality and time to market goals. It's up to executive leadership to determine an effective business strategy that includes thorough analysis of the opportunity costs of choosing one method over another.