The optimizations come in the form of data propagation, node processing speeds (sw optimz, hw utilization, etc). The scaling issue is w/ PoW blockchains, not their particular contents.
The issue really comes down to the sheer amount of data that must be stored on-chain. Moving and processing lots of data is slow, whether it's a ledger or state of a virtual machine.
data propagation is common to both, so it is irrelevant to the comparison. VM is the critical difference; Ethereum's TX processing single threaded & heavy because of it
