There are too many variables involved when anglers attempt to compare the angling quality of wild and hatchery raised salmonids, especially if the sample size is small. Water temperature is one physical factor as others have pointed out, if compared fish are caught at different times. Other factors that are not being considered include the unknown recapture times of these fish, the amount of time they have been in the river, how far upstream they are caught, the type of water they are caught in, their sizes, gender, etc.
Back to the point Matt made earlier in the thread, which needs to be corrected/expanded a bit. There are some confusion on the "fitness" which has not been pointed out. "Fitness", in human society, is defined by physical strength, body size and all the attributes that result in advantage for one in a competitive situation. "Fitness" in biology, when discussing organisms other than human, is not always referring to those "strong" physical attributes. The survival of the fittest, is not suggesting that the largest, strongest specimen in a population are the fittest and have the biggest chance to survive. Beside size and physical strength, fitness can be measured by the immunity against diseases, fecundity (the amount of eggs a specimen can produce), the ability to evade predation, etc. Biggest is not always best, but rather smallest can have their advantages under certain circumstances. Each fitness comes into play at a different situation. Situations are always changing, some years are more favourable for bigger fish, while other years are more favourable for smaller fish.
In nature, breeding within a population does not only produce "good genes", or fittest/healthiest offsprings. The process of natural selection results in a wide spectrum of genetic variations (big/small fish, fat/skinny fish, fish that get sick more/less easily, fish that spawn early/late in the season). This is nature's insurance policy. The population's offsprings will face many different situations as they begin their lifecycle. One situation may wipe the smallest fish out, or maybe the biggest fish out. Another situation may kill off fish that lack the defence mechanism to fight off a disease.
Artificial selection such as hatchery production tries to mimic natural production as closely as possible, but if repeated over generations, the genetic diversity will be narrowed and the population will be unable to handle all situations that they come across. We can assume the fittest fish are the biggest fish and only take big parents to produce offsprings so they will all return as big fish, but what happens if the artificially produced population comes across a situation in their lifecycle where conditions do not favour big fish? What if only parents from early part of the run are artificially mated, and their offsprings return early as their parents do in years when conditions favour late arrivers?
I hope that provides a better understanding on how genetic diversity is influenced by natural and artificial mating.