Curiously I have found UPS (via a broker, not direct) the best for cost to the US or Canada from the UK.
The tracking is very good, showing updates as it passes through each checkpoint. I've never had to claim on anything however.
Shipping into the UK, Fedex has been awful, I had to make an official complaint for a (non) delivery of a reel, and it was the second time I had problems like this.
USPS has pretty patchy tracking into the UK - it converts into the local UK courier arm getting into the UK - and the insurance is limited shipping overseas, which is a worry if the items are of high value.