There are certain benefits when you use a cash buyer; they can complete fast on the sale (usually between 4 - 6 weeks).This is due to the investors having cash available, no house chain and everything in place like solicitors and surveyors.
If you are not in a rush to sell and you are looking at achieving the highest price for your property then an estate agent would be the best option for you, however going through the more traditional routes like estate agents can be very costly and time consuming; normally about 1.5% - 3% fees and takes between 3 - 6 months, if not more.
The offer they make will be based on information obtained by extensive research in the local area, recent sales of comparable properties, similar houses that are currently on the market and will normally be in 24hrs.
They can offer to "sell and rent back" so the seller never has to leave their home, "sell and buy back" - this is where the seller is given the option to buy their property back and a set number of years at a reduced rent, or just sell and move on.
Most companies pride themselves on putting the customer first and making sure that they have all the information to hand before making a decision. I would encourage people to investigate all avenues of selling their home to meet their requirements.