You should use one of the Event cutoff types so that the record(s folder) can be cutoff once that event has occurred. Between event and event+time, that depends on how many different records folders (RF) you have to cut off. Event alone will allow for cutoff on each RF at the time the event occurs. Event + Time will wait for a specific date after the event happens. For instance, if your event happens on January 3, the event cutoff will allow you to cutoff the RF on Jan 3, and allow you to dispose of it on Jan 3, 7 years later. For event + time, after the event on January 3, you would also have to wait a certain time period (like to the end of the month) to cut off the RF. This means that any RF with an event in January would be eligible for cutoff on Feb 1. This makes it a little easier to cut off all the RFs at the beginning of each month and allow them to be disposed of all together 7 years later. 

Essentially, if you have a lot of RFs requiring cutoff within a given time frame, use event+time so you can cut them off and start their retentions all together. If you cut off infrequently, you can just use the event rule and retain each folder on its own schedule.