What is the difference, if any, between zyrtec, claritin, (loratadine) or allegra in their effectiveness for springtime allergies?

Same. Each of the medicines work for some people; others for other people. No one medicine works for everyone all of the time. Sometimes you have to try different ones to see which one works best for you.
All good. Zyrtec, Allegra and Claritin (loratadine) are all antihistamines that all work well for allergy symptoms. Before one takes any medications, they should check with their physician to make sure the are the appropriate choice.