If you are going to be installing tubing, choosing your tubing carefully is advised. If you are looking into the use of spiral tubing, here is a concise presentation of the pros and cons of using it, what is difficult about the tubing and what is advantageous.
First of all, by using spiral welded pipe, you can utilize your space. The walls of the pipe do not need to be thick because of the spiral tubing format. Because you will not need to have thick walls, you will have room for the other parts necessary to install. This is especially helpful if you are working with a small space.
Secondly, the installation process is not difficult. Connecting a piece of spiral tubing to another piece is much easier than doing so with a flexible tube. You will be able to install the tubes in a relatively short amount of time, so that will save you either labor cost or time of your own.
If you are looking into spiral ducting, you will have the additional advantage of better static pressure. This improved pressure (as opposed to the pressure in a rectangular or smooth duct) will allow for better airflow, meaning that the spiral ducting can do its work to provide you with the air you need, instead of "losing" air throughout the tubes.
Spiral duct can take more space; note that as mentioned above spiral tubing, as used for cars etc, can actually take less space. A rectangular duct can have a relatively short height while maintain a large width and keeping the air flowing. Meanwhile, a spiral duct, which is round, has a larger diameter. If you have a fourteen inch space for your tubing, you will not be able to have spiral tubing with an eighteen inch diameter, whereas a rectangular duct would easily be able to fit within those space parameters. This must be considered as it may be more space efficient for you to invest in a rectangular duct, which will depend on your situation.
Secondly, it can often be difficult to keep spiral tubing clean. The little crevices every few millimeters are difficult to completely clear out no matter if it is duct or tubing. On the other hand, a rectangular or smooth tubing can be much easier to clean out. You can simply use a power washer if your tubing is firm.