For the portable wifi penetrator what is the success rate ?

It depends on few factors including:

• Strength of target WiFi.
• Type of Encryption used WEP WPA WPA2 WPS.
• Sophistication of Encryption used.
• Frequency 2.4 GHz / 5 GHz.
• Quality of WiFi Adapter.
• Power of computer being used.
• Quality of Word Lists.