7Z mainly relies on CPU-Core performance, not I/O (memory), so it’s expected there will be no significant difference.
Cache impacts memory performance for random r/w.
Better to test with some membench, e.g. GitHub - ssvb/tinymembench: Simple benchmark for memory throughput and latency
Some example result for Odroid C2: ODROID C2 · ssvb/tinymembench Wiki · GitHub