Grafting onto different rootstock can produce different outcomes in the fruit. To continue my example, Seville sour orange rootstock is considered superior for flavor but greening is putting an end to its reign in all but parts of Arizona.

Planting in different locations will also effect fruit flavor due to environmental variables: temperatures, sunlight, soil, fertilizer, rains just to name a few.

How often and how they are watered and the kind of water effects the outcome as well.

Pruning can effect the outcome as can position of the fruit on the tree.

The initial cultivation of the tree can effect fruiting and fruit taste. If the root system is poor the tree may fruit in low amounts, late in life.... Poor branch angles can effect fruiting.

Do you mean are some trees of a specific cultivar better than others of the same cultivar? If so the answer is 'yes' because a lot depends on soil, care, pruning, etc.

Or do you mean are some cultivars better than other cultivars? If so the answer depends on what criteria you use to define better.

However, when I worked in an orchard commercially, we had 4 rows of Spartan apples all on the same rootstock and
planted the same time. A few of those trees produced heavily every year but the apples they produced were so small they fell thru the sizer while grading. Worthless except for cider.

We tried fertilizing and found no size increase. The trees were healthy otherwise. Virus? The few trees like this seemed healthy and showed no visual signs of virus.

I have the same issue on concord grapes. I bought 3 nice
healthy looking vines bare-root. The first produces normal
concord fruit in shape and yield every year. The second vine grows rampantly but never produces much as the
clusters have 2-3 fruits in them only. The third vine always
has gigantic clusters of grapes that are breathtaking to
see as they are so big and heavy.

All three of these concord vines ripen the same time and taste like Concord. If I ever propagate my own it will be from the vine with the gigantic clusters of fruit.

Just pointing out that sports, viruses ect can make a difference in a block of fruit all the same variety. Really important for the propagator to pick the best tree/vine when
grafting/budding or rooting a fruit variety.