The dollys are a larger option that have a hull supporting cradle and handle, which is used to push underneath the hull. The dolly's are sometimes an ideal carting solution for larger boats such as the Pro Angler and Island models. When selecting which wheelcart or dolly to go for it can pay to consider the type of use the cart is going to get, where it is most commonly going to be used and which model of kayak it is being used for.
The main advantage of plug in carts over dollys is that they are smaller, lighter (and in most cases store-able on deck while on the water) and simple to insert and remove from underneath the hull. The main advantage of dollys is that they will support the hull better and can be positioned anywhere underneath the hull, which can help to reduce how much weight is being picked up from the bow handle. They also have a wider wheelbase, making for a stable ride. However they are far too big to be stored on deck, and will have to be stored elsewhere (ie: your car) while on the water.
As a general rule, the plastic-spoked standard wheelcart should only really be considered for use on the lighter models: Lanai, Quest 11, Quest 13, Kona, Odyssey, Sport, Outback, Revolution 11, Revolution 13 and Adventure. The standard cart is a good choice for launching from solid terrain such as ramps, grassy and hard sand or soil banks. It is not well suited for use in soft beach sand.
The Heavy Duty cart looks and performs like it uses pnuematic wheels but they are in fact solid and therefore cannot be punctured. Thus it is the most reliable of all Hobie plug in wheelcarts. It will work with any model in the range but although it is better suited to use on sand than the standard cart, it is unlikely to perform well on soft beach sand or muddy banks under heavier models. The heavy duty cart uses the same frame as the standard cart, so if you have a standard cart you can upgrade it to a heavy duty cart by purchasing the heavy duty wheels.
The Trax 2 wheelcart uses 24cm pnuematic wheels that are intended to be soft and spongy in order to roll over soft terrain like beack sand. They work well under almost every kayak model Hobie make except for the Tandem Island.
The Trax 2-30 wheelcart uses 30cm wheels that are excellent for rolling over soft beach sand. They are the best option for Adventure and Tandem Island users that are launching and landing on beaches. They are rather large, however, and aren't terribly well suited to being stored on deck of the kayak on the water. Most users will find it best to store the wheels in their vehicle after carting the kayak down to waters edge.
Heavy duty 'Tuff' dollys
The heavy duty dolly carts are a good option for carting heavier and wider models across harder terrain. They are a lot larger and heavier than plug in wheelcarts but can make lighter work of carting the boat around. Unlike plug in carts these cannot be stored on the boat when in use. There are models available for Pro Angler and Island boats.
The beach sand dollys are the best option for carting heavy and wider boats across beach sand. These are also a lot larger and heavier than plug in wheelcarts (and are also pretty much impossible to store on the boat when in use) but can make lighter work of carting the boat around. There are models available for Pro Angler and Island boats.