Я не знаю, «отличаются», но как насчет:
require 'rubygems'
require 'differ'
original = "Epic lolcat fail bellmead drive!"
current = "Epic wolfman fail bellmead dr!"
diff = Differ.diff_by_word(current, original).to_s
puts diff # => "Epic {"lolcat" >> "wolfman"} fail bellmead {"drive" >> "dr"}!
captures = diff.scan /\{"([a-zA-Z0-9]*)" >> "([a-zA-Z0-9s]*)"\}/
captures.each {|c| puts "#{c[0]} to #{c[1]}" }