Great idea! Personally I had no bias towards either font, but now discovered that I do in fact like Helvetica a bit more (12 out of 20 times). Would be interesting to be able to see a test like that with statistics on how many chose each font for each logo.
Yeah, going into it I didn't know much about the differences between the fonts but was curious anyway. After getting a few wrong I switched to choosing which ones I thought looked nicer and started getting Helvetica more times. That reminds me I need to finish watching the Helvetica documentary.