Most people don't like to hand-water. It includes moving hoses and sprinklers around and usually can only be done when home. If you're lucky enough to have flood irrigation, you are also constrained by your scheduled time. An irrigation system frees you up from this.
Overhead Spray vs. Drip
Drip irrigation is always more efficient than overhead irrigation. Between our low humidity, high summer temperatures, and wind, you can lose 20% of your watering to evaporation. However, if you have a lawn or groundcovers, overhead spray covers the area more evenly. Nowadays, it is easy to convert overhead irrigation to drip. Costs can eventually be recuperated in money saved on your water bill.
In your landscape, whether it is existing or a redesign, the pop-up sprayers can dictate the placement of your plants.
In this example, because the green shrub is close to a sprinkler head, it creates a dry spot on the other side and prevents even watering.
In this example, the water blockage problem is not as severe, but any tall plants have to be positioned at a point farthest away from the sprinkler heads.
In this example, the irrigation system demands that tall plants go in the middle of the bed so as not to block any of the water.
In this example using drip line, the placement of taller plants is not constrained by the source of the sprinkler head.
Choices in Drip Irrigation
Drip irrigation is the most water-efficient. Here are a few examples.
There are different diameters and lengths of soaker hoses which affect the flow rate. The water seeps out evenly along the whole hose. Most soaker hoses easily attach to hose bibs.
Drip Line Choices
Some drip lines have emitters embedded in the hose itself. Other drip lines are made for you to put emitters in where you see fit.
This cutaway is to show the emitters embedded in this 1/2" drip line. You can also find it in 1/4" diameter. Emitter spacing varies, so choose the one that fits your needs. Most of these drip lines have a flow rate of 1 gallon per hour.
These emitters are used to place into the 1/2" poly tubing. Different colors denote different flow rates. You can customize this drip line so you could have areas between plants where there is no watering at all.
These are bubblers and tiny sprinkler heads which connect to the 1/2" poly by 1/4" tubing. They are completely adjustable. If there is a plant or a pot which needs an even higher flow rate, these are good solutions.