Like many things to do with motoring roadside assistance can be a matter of personal choice or experience. However, in order to judge how effective they are, there is one or two things you can do.
Read carefully through what the various organisations are offering, This is for comparitive purposes, and so that you can judge which is going to provide the most suitable service for you.
Read the small print carefully. For example, I know of one in the UK that provides for breakdown to home recovery. However you have to read the small print to find out that this provision only works if you are within 10 miles of home. Any further than that and you have to pay normal recovery rates.
Normally these operators will offer a number of different standards of service contracts. Make sure you choose the one that suits you. For example, if you do a lot of long distance travelling, which might include overnights, make sure that it provides for either accommodation if they cannot get you and the car home, or other form of transport to get you home.
Beware of overseas coverage. This is particularly a problem in Europe. I had international roadside assistance for travelling through France and Spain, only to find out when I needed to use it that the French motorway operators do not allow private roadside assistance companies to access their motorways. You have to get off the motorway first, and pay for the French to get you off.
Finally, you should always ask others, and your local consumers association, about the standard of service that has been received from the various operators. Recommendation is the best data to base your choice on.