Knives to the back result in a one-hit kill, incentivizing flanking unaware opponents this stealth approach is accompanied by a visibility meter so you can see whether or not you are visible. A blazing guns approach might be fun, but a difficult one to pull off successfully as the AI are crack shots regardless of range.
You can go in guns blazing from the start or take a stealthy approach. 2: Covert Strike breaks the mold by creating vast open maps to tackle how you want. It would not be unreasonable to assume that, as a first-person shooter, you'd be placed on a linear path to the end of each mission.
