[Dearth]

As most already stated it can be more difficult to maintain a smaller system but IMO the rewards are often way better.

Pluses

Easier to maintain
Easier to find a place to put a tank
Easier to see your fruits of your labours
No need to mix water every few days
Smaller fish are often more active
Huge water changes are not the logistical problem as in larger systems

Minuses

When things go bad hey go bad fast
Death of almost anything in a small tank can create issues within a matter of less than an hr
Evaporation is a major pain
Salinity changes can be huge if salt creep falls in


IMO having a much larger prorated skimmer will save you so many issues and I have found mine has saved my tank on a few occasions. I have a 33 gallon tank and my HOB skimmer is rated for up to 75 gallons and I have had fish death not noticed for up to 24 hrs and hasn't overly affected my tank.

Smaller tanks can be strikingly beautiful as it is both easier and harder to aquascape and coral again can be both easier and harder to maintain due to supplement and lighting needs of some types of coral

Unfortunately you are limited to smaller species of fish but again they can be way more active than the larger species and more entertaining to watch

This is controversial with many but I don't test my water regularly I think the last time I tested it was 3 months ago all I test usually is salinity every water change but in smaller systems water parameters can change fast so its a personal choice

I am slowly upgrading to a 95 gallon but my 33 gallon will always be my favorite