That surely makes a bit of difference. But, I corroborate the ideas about the clients' differing abilities as well. We run Microsoft and Apple workstations at

That surely makes a bit of difference. But, I corroborate the ideas about the clients' differing abilities as well. We run Microsoft and Apple workstations at work, but for Wi-Fi planning reasons, we keep some cheap laptops around as well. If we only test with our good machines, some issues will be invisible to us. And since I am in higher ed, many students cannot afford the high end computers, but they still need the service to work, so we have to test with cheap computers with terrible Wi-Fi chips, which reveals issues that are invisible to the latest Macs/Surface Pro machines.