How is the other machine family slow when it has the same resources? How do you identify such machine families?
They aren't the same resources. Different families have different generation CPUs and/or CPUs from different manufacturers with different performance. Just because instances are available with common core count and memory size doesn't mean an instance with 5+ year old ARM CPUs is going to perform the same as one with new Intel CPUs.
> How do you identify such machine families?
The AWS EC2 site...