What is the advantage of using Spot Fleet Autoscaling instead of AutoScaling Groups with a Spot Price?
Recently Amazon AWS released Auto Scaling for Spot Fleets (https://aws.amazon.com/blogs/aws/new-auto-scaling-for-ec2-spot-fleets/). Auto Scaling groups already allowed you to set a Spot Price to get Spot Instances at a discount instead of Reserved Instances.
As far as I could see Spot Fleets allow you to define the fleet capacity in terms of vCPU, mixing different instance types to achieve this. I don't think this can be done using Auto Scaling as far as I know.
My use case is pretty simple: use Spot Fleets (or Auto Scaling with Spot instances) to increase the capacity of my cluster at a reduced price while keeping the minimum required Reserved Instances just in case. I could duplicate my ASG, set a spot price and I'd be done, but apparently this functionality now also exists as part of Spot Fleets.
What is the advantage of one over the other? Are there any major reasons to switch?