The 1-2-1-1 press is an aggressive full court press with many different variations that can be made to suit your team and/or to give you an advantage over the opponent you're playing against.

1-2-1-1 Press (Diamond) Rules
No dribbling down the sideline.
No passes to the middle of the floor
No fouling on the trap.

Pros of a Press

1. More players get to play

Particularly in youth basketball, as you want your players to get playing time because you never know when a player is going to get a growth spurt or suddenly improve over the summer.  I even recommend having two units and substitute all 5 players each time.  It also means that depth matters, so who’s bench is better?  Most teams have a significant drop off outside their starting 5.

2. Exciting style of play, builds chemistry and everybody get shot opportunities

Every player will get a chance to score.  It’s fast paced and gets everyone involved.

3. Keeps teams from running their offense (especially if you’re shorter)

Press is difficult to prepare for because if they aren’t committed to it, it’s very hard to simulate in practice.  Even pressing teams find it difficult to break a press.  Opponents get shots that they normally don’t take at faster speeds than they normally take them.  Forcing a tempo upon the opponent they’re not accustomed to.  If you’re a short team, it’s great for preventing the taller players from getting a close shot.

4. It exhausts your opponents

Very few players like to be pressed.  Over time, there is a cumulative fatigue effect because it’s at such a fast tempo.

5. Great if your team can’t shoot or not very skilled

If you manage to force a turnover, it’s usually in the opponent’s half and often results in a layup. If your players aren’t very skilled, it also helps because you’re relying on defense for offense.  Trade in effort and stamina for skill.

Cons of press

Effort and stamina – This is an all or nothing system. It’s very tiring and requires players to sprint. You’ll need to coach effort and conditioning.
You need NASTY players – If your players are not aggressive then this is not for you.
Transition speed – If your players are slow, this is not for you.  Everything is about speed of transition. You need to force a high tempo.