Simple answer could be: the Bartlett may be precocious compared to the Anjou. It's just not uncommon for pears to take years to decide to bear. So as long as Anjou is otherwise healthy there may be no reason to worry.

But it's also true that pruning practices affect fruiting immensely. Heavy dormant pruning of vigorous trees into espaliers may delay spur formation on one variety more than on another.

But summer pruning encourages spur formation, and there are claims that this is particularly dramatic when done just prior to the solstice (Happy Summer, by the way.)

Just my best guesses- the more experienced may have better advice.

Mark is right, for pear trees planted only three years ago getting fruits is a victory. I have dozens of pears which are in their 8th year with no blossoms yet. The old saying "plant pears for your heirs" says it all.

Scott