Floor has several layers of Polypropylene (very thick) which needs sanding. I wont by using drum sander due to inexperience therefore looking for other fast machines. I can rent U-sand and 12X18 Clark vibrating sander at Home Depot which one is a better choice when it cones to speed and cause less dust? Are there other machines that i should consider (rental only)

Well, the Square-Buff machine will certainly do a great job for you, but you may be too old to enjoy it by the time you are finished.
Use a rental drum machine to strip off the old urethane, then complete the sanding process with the square-buff.