That depends on your needs, the destination, and your goals for a holiday.
Are you traveling alone, or with a family?
But, as for a direct answer to your question -- best season to travel is the season that you are prepared for.
(A little planning will help you have a "best time", without regard to the season itself.)
Among family and friends, there is always debate about when is the best season to travel. The fact is, the answer depends on a number of things. Where are you traveling to, what activities do you plan to do while there, and even when airline tickets are cheapest.