probably not a bad idea to purchase any additional coverage for whatever my AmEx premium car rental coverage doesn't cover
Alyssa: It's one or the other in Scotland, you have to refuse the CDW to activate the Amex policy, even if paid for, is not in effect unless you refuse the CDW and can prove it. Note that there are all kinds of activities that can void either insurance, drinking and driving, letting an unauthorized person drive, leaving the keys in the car, speeding, etc, there's no truly worry-free choice.
There's no advantage of choosing one international car rental brand over another.
These topics never resolve, because the people like me who use credit card insurance are happy and the people who buy the CDW are happy, and no one has much experience using both systems to compare. It's like the old argument about whether toddlers should drink 1% milk or 2% milk, they both work so there's no resolution to the argument, no best choice. Whatever you pick will work out. Caveat: using a credit card that has insurance that covers 100% of damage and then buying the cheap insurance with approximately $1800 deductible is stupid because you have paid for the insurance and then have voided the free coverage by doing so, getting the worst of both systems: paying for insurance and then also paying for the repairs up to $1800. Either learn your credit car policy and follow it, and carry it with you, or buy the super CDW.
A few warnings about driving in Scotland:
The driver sits on the right side of the vehicle so if you get a shift you will use your left hand to shift the transmission.
The main highways in the highlands have a lot of 1-1/2 lane bridges with tourist coaches and trucks bombing down the middle and taking up the full width of the bridge, the sign for this is oncoming vehicles in middle of road. The upper sign is showing the lane constriction at a bridge or underpass.
Things you will miss driving internationally:
Using a center yellow stripe to separate directions of travel, this North American norm is used in Norway, but not the UK or mainland Europe. So there's no quick way to check if a road or street is one-way while you are using it, so be sure to read the signs before entering the roadway. People park on the wrong side of the road so the direction the parked cars are facing can't be used for this purpose.
The most common damage to a car is scraping the hubcap on the curb while parallel parking, and while this type damage would be ignored in the US as normal wear and tear but there's no guarantee that will happen internationally. Also, the rolled-face curb that's universal in Minnesota and prevents this damage from occurring (the curved face lifts the tire up and leans the hubcaps away from the curb face) is not so common outside the Midwest, and rarely seen internationally where curbs are usually vertical, so don't rush parallel parking to get out of the traffic stream and stay clear of the curb because it is unlikely to have the forgiving design that you are used to.