I shop first for the features I want, then the size, then the color, finally by price. The features I want are:

1. A rating greater than 1000 joules with a hardware replacement guarantee.
2. Look at your load and add 40% then make sure the stated capacity is adequate.
3. Decide on cord length before stating your shopping.
4. Look at your mounting options and consider how accessable your plugs need to be. What orientation will work best with your plugs. I usually try to avoid the 1 foot extension cords but with many PDUs you are kind of stuck. Personally I like to install on desk legs to keep clutter hidden and off the floor.
5. I usually avoid the squid because of the messy installations it forces but it can work well if you have a lot of ac adapters.
6. Most USB ports on power strips are super slow and require longer cables to use than adding a power bank or hub with power built in. I usually don’t consider them when shopping.
7. Don’t forget plug shape. Whenever possible I prefer the cord to end perpendicular to the prongs and the cord to exit 45° to the orientation of the slots. This keeps the other plug free. This point is most relevant in North America.