Without question, this is the most asked question regarding our portable garden hose reel models. The primary differences involve balance, mobility and price.
First, it will buy you a bit more 'non-tip' stability. The two additional tires out front adds another 7-1/2" to the width of the front part of the frame and makes it slightly more stable than the 2-wheel model. Also remember that another significant factor with regards to the hose reel's tippiness has to do with how tight you set the tension on the adjustable cam-lever brake.
Second, the Quad-Wheel Kit allows to you maneuver the unit with a simple push/pull action (like a grocery cart), rather than the tip & push/pull action of the 2-wheel cart. The 2-wheel model will require you to balance the unit while either pushing or pulling it to the desired location. There really is no balancing involved with the 4-wheel model. However, unlike a grocery cart, the 4-wheel model does not have front wheels that turn. So you'll still have to either lift the two rear wheels, or the two front wheels, in order to change direction with with the 4-wheel model.
The two extra tires on the front of the 4-wheel wagon does add about 8 more pounds that you'll have to lift-by-tipping, in order to change direction.
One last point to consider is that you don't have to make the decision right now. The Quad-Wheel Kit is an optional upgrade that can always be purchased at a later date and used to easily upgrade an already assembled 2-wheel cart. For more details, check out our Garden Hose Reel Cart and the Garden Hose Reel Wagon pages.