Both let you do full operator-enhanced tag searches but their syntax and other features differ.
MatchTagsPlugin lets you set up a new search field which displays its results in a new tiddler in a configurable format and will search only tags using a syntax like this:
excel AND (macro OR script) AND NOT virus
YourSearchPlugin modifies the existing search field to support a richer query syntax (and, optionally, a new results popup) and you can specify that a given entry should only match tags by prefixing it like this:
#excel (#macro or #script) not #virus
You could also poke around on TiddlyHub to see if anything else might meet your needs.