GenStake is another PoS/PoW coin that runs much less CPU and memory than HBN. 2GiveCoin runs with very little resources but is much differently structured kind of PoS/PoW coin. Hyperstake and Truckcoin are also lower in memory and CPU use but do not use PoW. (Truckcoin runs higher on CPU use) The GreenCoin daemon runs with very little CPU and memory use but is also PoS only.
CPU will be solved, so take that out of the equation.
But with memory, you have to compare apples to apples. We are at block 5.2 million. What are those coins at? When HBN was only at block 1 mill, it used a reasonable 300megs. More blocks, more memory.
Run a spread sheet on Memory vs number of blocks, and tell me which is the lowest. We can go from there.