VL-Hot is a mounting tool by Joe1942, and HAL is a hardware polling service. They both serve to simplify the device mounting process for users, however they differ greatly in functionality. VL-hot is a great minimalist mounting tool for non-CD/DVD devices, however it seems there is a caveat when the device is plugged in upon boot (as you may have discovered). HAL is a hardware polling service that constantly polls the system for new hardware, thus it is able to detect when a CD/DVD is inserted and mount it accordingly. The drawback is that it is constantly polling your system for new hardware using resources to accomplish this. On a system with plenty of resources you may want to enable HAL. If you want your system to automatically mount your cd/dvdrom drive when you insert a disk then you should enable HAL. If you want to save some resources and mount cd/dvd drives yourself then VL-hot is for you. This explanation is very generalized and simplistic but serves to illustrate the point. Others may be able to add more to the picture that I can ATM.
You can switch between the two by accessing: