Thumbnails give variety
The reason: process of thumb-nailing in a big quantity give a number of advantages:
It give a good start towards the design process
When a designer is creating thumbnails, he is not restricted to any structure and, process he can design thumbnail in a process similar to lateral thinking, completely free flow and unstructured, this result in a variety of designs which is the key benefit of the process.
During the process the designer put down every possible idea he can come up with and so brainstorming happens and he put down all his thoughts related to the design problem in hand.
Thumb-nailing down also allow you to push your mind to come up with different ideas for the same problem, this also stretches your mind to think of new solutions, which show up after putting down the most common ideas.
The value of thumb-nailing lies in the following
The designer don’t have to invest a lot of time on any particular design in the early stage, so saves some work.
The designer can showcase his ideas to the client and get his feedback, this is an important step towards understanding the clients requirement and choice.
More number of thumbnails provide you with a lot of raw material to think about the design problem, how each solves and fits in the current design.
The early stage of Conceptual thinking, which is putting down the basic idea in the form of thumbnails or thumb-nailing can be done very effectively without computers. At this stage the mind is flowing freely and is pushing you to think in every possible directions. A mental map of the design problem in hand goes in all directions, here a computer can restrict more than adding to the process. Because at some time you might want to express something in 3d, something in different shades, shadows, colors and different scale, these aspects of thumb-nailing is very efficient when the mind works with eye and a hand and Pencil in perfect synchronization. No computer can beat the speed with which a mind can come up with new ideas.
At a later stage when you want to try different color schemes to your concept or thumbnails, try with different layout options etc a computer can be an effective tool. With photo editing softwares and 65000 color options. you can almost see all your concept in multiple formats and layouts in no time and judge them for their effectiveness. So this is place where a computer can help on conceptual thinking, to finalize your concept, to experiment with different colors, shades, tones and dimensions.
In conclusion I would say the concept creation process is faster when doing with hand but the editing can be effective when doing with a computer.