I saw this in their forums, checked it myself, sure enough, with modern CPUs and AVX running Asteroids@home is more efficient power wise on CPU than on GPU. Ryzen 3950X blows an RTX 2080 out of the water on throughput per watt. Similar for i5-8400s, that low watt CPU beats out a similarly powered 1650 in throughput per watt.
So if anyone is interested in crunching this project, CPU seems to be the way to go. Speed is not a factor here, throughput is, and if you want to do it power smart, AVX CPU prevails over GPU.
Use of HyperThreads not recommended