Prioritization of tasks, or leads, is a false comfort that you are optimizing your production results. The real truth is that you are allocating time and resources to guess at what may be more valuable if you spend time on or accomplish the task.
This is even a bigger fallacy as it pertains to sales leads since you have no insight into a buyers intent. You may prioritize a larger deal higher than smaller, but you may be able to equal revenue with smaller lower decision threshold accounts.
The key is determining whether you are or are not going to do the task and then getting immediately to working the list. Determine whether you are going to work the lead or not and then pick up the phone.