Using Dot 5 in 2 out of three cars, I don't see and performance difference but I have no worries if I ever refill and spill a little or have a seeping gasket...
69 RA III T/A Auto 69 Sprint vert 3speed ( sold to a new home) 69 350 coupe ( new home in Denver) 69 350 HO 4spd
Supposedly DOT 5 will not take on water from moisture in the lines over time. I've always heard that you should flush the system when changing from DOT 5 to DOT3/4. I like the response from maxepr because spilled DOT 3/4 will wreck any paint it touches. I inadvertently switched back to DOT 3/4 without ill effects even though I didn't flush the system. However I drive that car only about 500 miles per year. My conclusion is you can switch, but why?