When starting all the devices I checked used the same technique; drop; delay;drop;delay and I used this method for an an early version of the dropController. I as progressed I found it difficult to get the drops I wanted due to how the Arduino handles delays. Switching to start and size times means you can have multiply drops active at the same time and it gives more control over the drops. For example, should you want, with the dropController you can have 9 drops all active at the same time. This is not possible using delay().
The Arduino delay() command blocks the code meaning the Arduino can not do anything else while it is waiting. If you want to know more about this look in to “Arduino delay”, “Arduino blink without delay” and “Arduino doing more than one thing at the same time”.