M390 will hold an edge much longer but will be harder to sharpen, Elmax is a bit easier to sharpen but also will not hold an edge as long. I think as far as chipping go the M390 might be more likely to chip, simply because it is harder and thus more brittle. I've used Elmax for EDC and it is a great steel, I've only had an M390 blade for a couple weeks, so not enough data to really make a comparison.