Using very old versions of Solidity prevents benefits of bug fixes and newer security checks.
Using the latest versions might make contracts susceptible to undiscovered compiler bugs.
Consider using one of these versions: 0.7.5, 0.7.6 or 0.8.4.
(see here)
- Old vs New Versions
- Old: Bugs, Time-Tested
- New: Bug-fixes, New Bugs
- Old: Less Features
- New: More Features
- Optimal Version
- Security vs Functionality