First of all, thank your nephew, for his service to our country, and tell him that we all appreciate people like him, and the things they do for the rest of us.
About the knife, I am in a similar situation with my cousin, I have some different brands, all are similar, and I have been ordering a couple of everything that interests me. Because I am going to let my cousin pick which one/ones he wants, before he goes back over to afghanistan, for his 3rd tour. I gave him a Glock field knife (before I knew, what I know now, about knives), when he went on his first tour, and he liked it, but said it would not hold an edge very long, and he could'nt sharpen it real well with the file on his MT.
from what I hear a knife gets gets used more for opening MRE's, cleaning finger nails, and prying open crates (when nothing else is available), and just everyday passing the time. more than anything else.
Again a big thanks to your Nephew.