The bottom line is this: you'll be taking down terrorists one at a time in Splinter Cell: Blacklist and the game is supporting your ability to do this in so many ways. The Ghost, Panther and Assault playing styles come with their own gear, their own tactics and their own rewards. You just have to decide how you want to run your anti-terrorist campaign. And don't think you have to choose one style and stick with it. The game is segmented in such a way that you can do one part of a mission as, say, a Ghost --staying undetected, knocking out enemies instead of killing them and hiding bodies-- and then follow up on the next segment in more of an Assault style --you make sure the enemies see you and you smoke them all with superior firepower and explosives.
The right equipment isn't necessary to use those play style but it sure makes things easier. If you're geared up with heavy armor, a shotgun and lots of grenades in anticipation of an all out gun battle Assault-style, that doesn't mean you can't still sneak around. You'll just be clanking around in your armor so you have to be extra careful of spooked guards and when you do engage it's tough to show restraint and knock a guy out when you've got so many toys to use. Similarly, going with a Ghost configuration with all kinds of tear gas and a silenced pistol doesn't mean you can't take on a room full of heavily armed terrorist. It just means you'd better be super accurate with every shot and quick with your moves......which can be very fun.
Check out this sequence of Gameplay clips for Splinter Cell: Blacklist and see if you can recognize the Ghost, Panther and Assault styles of play.