For min/maxing, I'd still choose the gnome.
Let's say the Human above can take an 18 Cha, 10 Con, and 14 Dex, and Toughness. That's 7 hp, 12 AC, +2 attack with the crossbow.
Now, let's say you're a Gnome, with 18 Cha, 14 points in Con, and 10 Dex. The 14 Con becomes a 16 Con, and you've got 7...