More disadvantages with a barrel compared to glass, stainless steel, or plastic:
1. More difficult and risky to buy used.
2. More apt to leak.
3. Require more maintenance (rehydration, sulfur sticks, or always keeping full, etc.)
4. More practical in larger sizes that cannot be easily moved or lifted.
5. Must be checked and topped up continuously to prevent over oxidation.
6. Wines you don't want to undergo an MLF cannot be put into a barrel which has had an MLF wine in it before.
7. Not practical for apartment dwellers. You definitely want a yard/drive wayand a garden hose.
8. After getting your first barrel, you'll be hooked on them and not want to use carboys anymore.