People are right, they are more difficult because of swings. You really have to keep up with top off and water changes, otherwise a crash is likely.
Look at it this way, if you lose a gallon of water from evaporation in a 125 gallon tank, it doesn't cause many problems because its less than 1%...you lose a gallon of water in a 14 gallon nano, your parameters just changed dramatically. For a fish only tank, not as much of an issue, but if you want to keep corals and other more difficult creatures, a larger tank is best.
If I were you, I would look into a Red Sea Reefer tank or something similar, as it provides you more water volume with the included sump (where you can hide all your extra equipment), includes an auto top off device, and will help make the transition a little bit easier!