For my group (Okanagana) there does appear to be some host specificity on what they’ll lay their eggs on, and in some cases they will only use a single species of plant. The host is unknown for the majority of Okanagana species though, and some of the northern taxa such as Okanagana rimosa have been shown to be associated with 5+ species of trees.
Periodical Cicadas (Magicicada) don’t have a preference for tree type that I know of nor do the “Dog-day” cicadas. I don’t think Magicicada use pines, but I could be wrong.
Basically the answer is: it depends of the group/species about whether there is any kind of preference.
In your yard, is there different sun exposures between the two Callery Pear? Cicadas do like to be in the sun when they can, so that might be a bigger aspect of what you are noticing rather than whether or not they’re laying eggs. On that related note, isn’t that ‘pear’ an introduced species?