Even if using Aes needs to spend a little bit more, it gives to you more animations and more realism on the airport. You couldn't have this with only the effect of default airports of moving jetways which sometines don't even work well.
With a single pack of AES credits you can use it for around 3 big airports or 4-5 middle size ones. It's a good deal and you will have fonctions like: De-icing, boarding, deboarding, catering, cleaning trucks, stairs, cargo cars, marshallers, pushback, etc.
It's quite a nice tool.