The pump drive is not always what fails, it is usually the pump. On a direct drive machine There is no drive, the motor hooks up DIRECTLY to the pump. The other types use belts/pulleys, or Gearboxes to turn the pump. The pumps used in these systems are designed to pump water while they turn at lower speeds. This lower speed makes them not work as hard as the direct drive does, They will last longer if taken care of. They do, however, have more components so there is more to maintain. The pump drive in belt and gear drive machines can fail. There is no drive system in direct drive units so I guess the "pump drive" in the direct drive system can never break since it doesn't exist.
I hope this confuses you even more
LOL
One other drawback to direct drive are the pump choices. You can find many different flow rate (gpm) and pressure (psi) for belt and gear drive pumps, direct drives are much more limited. For decks I would suggest a higher flow and lower pressure. There are not as many high flow direct drives available.
I have some direct drive machines and they are fine for most uses. As long as you have a good water supply and keep up with maintenance you should be ok with it.
If only we knew where you were from we might be able to help you find a good local equipment dealer.
I would recommend that someone with limited knowledge in how these machines operate get their machine from a good dealer other than a big chain store. From your questions, I believe you fit into this category. The dealer can help you out with repairs, maintenance and answer your questions. Home Depot can read the box to you (maybe).
later