They talk about the different utilization instances, but I can\'t find a single place that actually states what the difference is between a light utilization Large instance or a
The instances are the same. It's just a pricing difference so you can save money if you know you will be using the instance a lot, by paying an upfront cost.
You pay more up front for a heavier utilization instance, but you save more in the long run assuming you have it running all the time, because the hourly rate is cheaper.
So it's just a matter of how much you will be using the instance (having it running) that determines which type is the best value for you. If it will be on all the time for a year or 3 years, then a heavy utilization is definitely the cheapest option.