I've had issues with FedEx, they overcharged me once and then wanted £50 to amend the invoice??? Never used them since.I raised it with both, received the original paperwork from Sideshow and sent it to DHL and quoted the law. They refused to do anything about it.
I used to select FedEx because I have an account with them, so don't pay any admin fees. However, FedEx is more expensive than the admin fees themselves now. DHL was the cheaper option, yet in the past FedEx has agreed to numerous refunds from overcharging.
I think all the couriers are crooks.
DHL all good so far but it's only a matter of time.