The key with the egates is, before joining said queue, survey it to look for people staring at the front and back of their passports to work out if they are eligible. If you see two or more of said people ... avoid.

Those people will take more time than anyone else to get through ... they'll put the passport in wrong ... they'll not look into the camera ... they'll not realise the green light means 'you're ok to enter this booth' ... they'll not realise it's one at a time ... they'll not realise you have to actually do anything when you enter the booth ...

Not that I've seen all this and been frustrated or anything ...

My other golden rule of thumb is that the length of the e-gate queue with it's much shorter 'back and forth' shouldn't have a higher count of back and forth populated than the normal queue. If it does - avoid.

But I've also made the fast track silver/gold mistake. Got turned away after I got given a ticket on a flight. CC in CW hadn't even asked - just handed them out. Was most disappointed.