It's not a matter of which is better and which is worse. They're both equally used in different aspects. Sure, most people only see one of them in their lives. Those living in metric system see SI using more than anything else, and vice versa for imperial units. But that's not to say one is better. Once you get past that and start doing complicated math in whichever field you are, unit conversions becomes first hand. The rule is simple, answer the question in the units it was asked in. If it's imperial, you're free to convert it to metric for your own ease of calculations, but just convert back at the end. Sure, temperature in Fahrenheit might seem like a useless scale to a lot of people who are used to Celcius and Kelvin degrees (K = C + 273.15), but Fahrenheit is useful in that a lot of calculations and formulae use Rankine degrees (Ra = F + 459.67). So it's not entirely useless. There are several units of Work (ergs, dynes, joules) that can be used depending on the situation that you're in. The more recent papers that you find and formulae and what not, probably use the metric system since that's the most commonly used system now. However, we don't reinvent the wheel every time, so the formulae that were found 50, 60, years ago, remain as they are, and they probably use the imperial unit system.