Painkillers increasing on re-spawning in Max Payne 3 ..

The silenced weapons you come across in the single-player campaign will have a very limited one-time use. In the levels that you get them, you're only able to use it (with any effect) for the very first fight you get into. After that, every enemy you encounter will be forced on you.

There's only two instances of when you get a silencer, at the Tiente Docks in Chapter 5 and the Crachá Preto Hotel in Chapter 12.

In chapter 5, you start the mission with the silencer and will come across two guys loading a truck. If you are able to successfully kill them both quickly without them being aware of you, that will be the end of them and you can move on. If they see you, more guys will be alerted and will attack you.

But even if you were able to kill the first two quickly, there's no hope for you to be able to stay stealthy for long. In the very next section, you will be forced into a firefight. You will be hiding behind a window (in a very awkward position) with two guards being suspicious of your location. There's no way to get away from that position without them seeing you. Going into bullet-time in the hopes of shooting them first will be fruitless as you will have to break the window and that will alert everyone. There's no hope of staying stealthy, every wave will be alerted of your presence.

In chapter 12, you will fashion a silencer with a bottle taped over the muzzle. Again, after exiting an elevator, you will come across two guys. Again, you will have an opportunity to take them out quietly but it won't matter. There's two more guys in the next room that will rush in no matter what. You can kill them quickly but it's not going to matter, nobody else is around.

After dealing with those four guys, you'll see a guy standing in a hole in the wall. Kill him or not, it won't matter. The group of guys in the next section will be alerted.

In the end, the silencer is just a waste. You only really have one opportunity to use it where it affects the fights you are able to avoid. Otherwise, every fight you do get in you are forced into. So don't hold your breath thinking you can play through the game like a ghost, it's just not going to happen.

Any gun is good, it's just your playing style that matters.

If you're a tactical-kinda guy, you should think about using a SMG.
If you're pretty good at aiming, rifles are the way to go since they give you a ton of damage but high recoil, which shouldn't matter if you are good at aiming.