There are many factors to consider when choosing a wedge for splitting wood. The most important factor is the type of wood you will be splitting. Softwoods, like pine, are easier to split with a smaller wedge. Hardwoods, like oak, require a larger wedge.
Another important factor is the size of the log you will be splitting. A small log can be split with a smaller wedge, while a large log will require a larger wedge.
The angle of the wedge is also important. A steeper angle (60 degrees or more) will make it easier to split the wood, but the wedge will need to be driven deeper into the log. A shallower angle (less than 60 degrees) will make it harder to split the wood, but the wedge won't need to be driven as deep into the log.
Finally, consider the weight and length of the handle on the wedges you are considering. Heavier wedges are more difficult to swing but can generate more force. Wedges with longer handles give you more leverage but can be unwieldy if they're too long.