What are the strengths of roman numerals?

Answer 1

There are few, if any strengths. It's non-positional notation was not ideally suited to computation (although it was possible), so notating individual numbers and lists was its only real strength. Although fractions were possible, they only dealt with duodecimal fractions (1/12ths).

The Hindu-Arabic numeral system can trace its origin to around the 3rd century BCE, about 100 years after Roman numerals were conceived, so it's not as if Roman numerals were the only system available, and there were many others that pre-date both, by a long way (at least 3000 years BCE).

The Hindu-Arabic system was introduced to the west in the 5th century CE, but it wasn't until the 9th or 10th century that it became the first base-10 system, with the inclusion of the number zero. This revolutionised computation, but, even so, Roman numerals were still commonplace up until the 14th century, so it clearly still had some merit associated with it.