Comparing the Avro RJ-100 with the 737-500 is like comparing an apple with an orange. No difference between the 2 fruits, when tastes like a regular fruit, while the other is a tangy citrusy fruit.
They're 2 completely different aircraft designed for different purposes, even though capacity wise they are similar.
The Avro RJ-100 is truly a special niche aircraft designed for short hops, and to fly into unprepared or extremely short strips where other airlines cannot fly into.
Infact, the Avro RJ-100 can fly into places a CRJ-200 cannot.
The Avro RJ-100 is really a special aircraft designed for special purposes, which is why they are not very popular by airlines. They are also relatively expensive to operate, but there versatile abilities are what made them sell.
The Avro RJ-100 is probably the best aircraft when it comes to short mountain hops. No western airliner beats it. This is why it's popular by airlines like SWISS and Air Wisconsin.
Although airlines have been using them on routes a CRJ or a 737 could go these days as mountain flying is limited to only certain areas such as the US Rocky Mountains, the Alps in Europe, and the Himalayas in Asia.
"Generosity is giving more than you can, and pride is taking less than you need." - Khalil Gibran