M390 has some qualities which make it better than the s30v which are: 1. M390 is a newer and improved prototype of super steel than the S30v. 2. M390 has better edge retention properties than the S30v. 3. M390 has better abrasion resistivity than the S30v. These qualities make it a perfect choice for knife lovers and worth the extra money. Reasons to choose s30v over M390: 1. This was the first super steel type which is used for knife manufacturing. 2. S30v is much easier to sharpen than the M390. 3. S30v will cost you much cheaper than the M390. Both the steel are best in terms of wear/tear resistance, toughness, and edge retention but M390 is way better in most of the parameters. Choose any one of them according to what matters to you most.