I liked the answers given here. I wanted to add 2 specific examples not mentioned yet, along with an analogy, to help add to what has been posted.
As mentioned, the design of a tactical military jet is a trade-off between effectiveness and ineffectiveness for a given mission. A simple example is that of a light attack bomber. Precision bombing would dictate a stable platform, i.e. low roll rates. The A7-E had a high mounted wing to increase stability in the bombing run.
As a bomber the A7-E was unsurpassed. I was in a bombing derby in 1985 with the newly deployed F-18's. The F-18 had an advanced delivery system, and still I was able to match their CEP bomb for bomb. But the A7-E it was not a fighter. It did not have the thrust-to-weight ratio that a fighter did, and so was at a disadvantage in ACM with an adversary like the F-18.
The A7-E also operated off of carriers based at sea, which can complicate the choice of design. Bombers want long legs to reach inland targets with heavy payloads of bombs, and so fuel efficiency is of particular importance. The A7-E delivered in this respect, and burned around 6-9K of fuel per hour at sea level and military power. This got us up to around 750 mph, which is just below Mach 1. But long legs are not only needed to reach inland targets from the ship, they also serve maintaining real-time surveillance of threats surrounding the carrier out to 200 miles.
When the A7-E was replaced by the F-18, which has the shorter legs of a fighter, the carrier lost the ability to have real-time surveillance of surface threats out to 200 miles. So here you can see the tradeoff affecting the strategic concerns of the battle group.
My last comment concerns design choices for the F-14, which was designed as a long-range interceptor. I knew some Tomcat drivers while stationed aboard the USS Nimitz and they told me an interesting vulnerability that you might not guess. The F-14 interceptor has a variable-swept wing, which is an attempt to mitigate the interceptor design with that of a fighter designed solely for air-to-air engagements. Yet when the Tomcat was in a turn, and G's applied, the wings swept forward making it a barn door in the sky. Easier to spot than let's say the F-16. There was a saying in air-to-air combat something like, "The first one to gain sight wins the fight." So we see here another choice where survivability is sacrificed for the interceptor role.
Finally, consider the evolution of the design of 12 meter class sailing boat. The design of the 12 meter class boat must obey the formula (America's Cup formula):
Where L is waterline length, d is the difference between skin girth and chain girth, S the sail area, and F the freeboard. Designers are free to choose these parameters any way the want as long as when substituted into the formula in comes in at less than 12 meters. Make a sailboat good in all wind conditions, and then in strong winds it will probably be beat by a boat built strictly to win there.