What is the difference between primary coverage and secondary coverage on a travel insurance policy? Which is recommended for short-term travelers?
Primary travel insurance pays for any claims you make straightaway up to the coverage amount you have while secondary travel insurance requires you file your claims with any existing insurance provider you have (medical insurance, for instance) and once that coverage is exhausted your secondary travel insurance kicks in.
What's better depends on which specific plans you are comparing and how much savings it brings you. Some medical insurance plans (non-travel) may not cover you for costs incurred abroad. Additionally, if you buy secondary insurance and have to get in touch with another insurance provider, you need to consider the hassle of having to file claims with an insurance company that may not have a dedicated support team to handle claims coming in from travellers and process them quickly enough.
If you're going for short-term trips, at least in Europe/Asia you will find it less hassle to buy a per-trip travel insurance policies which are often quite cheap.