I would tend to think WireShare's default filters reduce the search results. For example, Wireshare automatically filters out the following file extensions: html, asf, asx, wma, wmv, etc.
Also search type (such as audio or video) filters out results not matching the type of file.

Edit: Misread the question as comparing number of results. Three possibilities I can think of: both clients are outside each other's search horizons. It's also possible either one ignores search results coming from same address. Wireshare's search results will show files it already possesses either bottom of list or hidden depending on your settings for searches. I've also experienced same issue of not finding shared file(s) between my own two different apps.

As for search result numbers, it can vary depending on the dynamics of the network and that includes the quality of connected peers or others within the search horizon. For example, if one were connected to a forced-ultrapeer that's firewalled, that might create a dead end for one of the avenues of the searches. This also relates to poorly performing ultrapeers within the same search horizon, keeping in mind the search horizon will gradually change over time as ultrapeers drop out or log out and others replace them.

Question of whether both your GTK & WireShare are connected as leafs or ultrapeers or one in each category. It makes a notable difference in search results tallies. That's something I've noticed since testing it on an annual basis for over a dozen years. A little known fact. The original developer of FrostWire from Germany and major contributor to the LimeWire code over many years mentioned this roughly 18 years ago on this forum.

WireShare also automatically filters out all results coming from the common spam-bot; cleaner search results, less junk.