Bryston 5B THX or non THX ?

That is the question!
Is there a difference between my ST THX built in 95, or my neighbors built in 99 that is ST non THX badged ? Other than the smaller vent holes in the top lid, and the toggle switches instead of slide switches for ballanced/non ballancedsections, I can see no difference. Any help will be appreciated.
No difference sonically. The THX has a 12 volt trigger, that's it. I had 3b st thx which is the same as a regular 3b st.