This is a difficult question to answer as it will depend on the property in question as well as on the needs and goals of the buyer.
Land for sale in the Cayman Islands does make an excellent investment, as land does not depreciate, and, if anything, will trend upwards in value over time. Land also requires little to no maintenance at all; making it sort of like cash in an interest-bearing account, except that it is immune to inflation and other fiscal mismanagement.
Developed properties, however, can also be an excellent investment, especially for those that plan to become Caymanian permanent residents, who wish to raise a family here, or who simply come here for work.
Buying a house in the Cayman Islands will give you a place to move into on shorter notice, if not immediately, with little to no extra work. Also, if well kept, a house also has the potential to increase in value.
Some prospective buyers might also be interested in the purchase of a condo, as there is less maintenance involved in buying a condo and they usually offer a wealth of shared amenities.
So, ultimately, neither is better than the other. It just depends on what you expect to get from it.