When you rent "points" what actually occurs is that you rent a reservation that the other member makes in your name. Thus, no points are actually transferred to you and that transaction thus does not count as a "transfer," which a member can do only once per use year.
A member who is doing rentals of reservations can do multiple rentals per year. A member who wants to transfer points to someone else is instread usually trying to get rid of a a precise number of points he cannot use and has to do it all in one trasaction because he is limited to one transfer per use year.
It is usually harder to find a member who will transfer to you the points you want both because there are fewer persons trying to transfer points than doing reservation rentals, and because those trying to transfer points are usually trying to transfer more or fewer points than you want.
As to advantage, some members are sometimes looking to rent a reservation rather than borrowing because they either do not have enough points to borrow or they want to take a trip now and also use those points in the next use year for another trip. In fact, it sound like that may be the position you are in.