Peter Lin, who works on the JMeter project has performed some benchmarks that indicate htmlparser is 40% to 600% faster than JTidy:
10 20 30 40 50 100 500 Yahoo Cnet
Htmlparser 80.0 126.4 160.4 200.4 236.4 400.6 1630.2 474.4 1251.8
Tidy 498.6 531.0 626.8 658.8 687.0 849.4 2319.4 965.2 2049.0
Delta 6.23 4.2 3.91 3.29 2.91 2.12 1.42 2.03 1.64
Full details are available in a zip file.