Some features have become standard on all travel luggage. Wheels on luggage are now the norm; it is odd to think there was a time where all luggage was carried, or required a trolley. But despite handles, wheel and zippers being standard not all luggage is created equal.
Some surveys show the important factors in travel luggage. Durability and wheelabilty were commonly mentioned concerns.
Two wheels of four? The four wheel versions are easy to manoeuvre, whether they are behind, in front or beside you. And they do not need to be propped up on a flat surface. The downside is that they will roll away on a slope.
Two wheel bags is easy to pull behind you, and will stay propped up on most level or slightly slopped surfaces.
Wheel can be a week spot. It will be a great inconvenience if the wheels break off when traveling.
Externally mounted wheel are more likely to break, especially with rough baggage handlers. Wheels that are built into the frame are less likely to break, but they may also harder to replace. An external wheel might be replicable.
A wheel that spins in 360 degrees will suffer more wear and tear than a recessed wheel that only moves forward and backward.
The material a bag is made of has a lot to do with the durability. A soft material will take a fair amount of internal load, but may be subject to external damage.
The weight of the material is also a consideration. Airlines limit weight more than size. Aluminium is durable but relatively heavy. Fabric is light but can suffer damage. Hard plastic and carbon are a good combination.
Check the range of bag available. There is always a good option.