It's just quicker. I could loop a section and cycle through testing out the different composting modes very quicky to see what works best. Having to click and choose each time to change it creates many more mouse steps. AE and photoshop have this ability and it makes for quick work. It would be great if once the composite menu is opened you could just click your up/down arrows keys to change modes just like how it works with Vegas effect presets.
Thanks for listening, Vegas is a fantastic program and I look forward to seeing what you guys come up with next.