(1.) is not entirely true. I did test 3-level hash with approximately 20 keys per level. I did try to clone the whole thing, only two level slice and finally 1 level leaf. here are results: 1level "leaf" hash: Clone is twice as fast as dclone 2level hash: dclone is a slightly faster (assume the same) whole 3level hash: both are nearly the same (very slight ~1% advantage to Clone) everyone can setup own test but I think Clone has slight advantage only for very small structures. I would go with dclone. my 2c :) good luck!