Series vs. parallel speakers in back loaded horn

[7n7is]

I built two back loaded horn speakers based on the plans from Audio Magazine Nov 1955 and put one 8 inch speaker in each cabinet instead of two as shown in the article. They each have a two way crossover network (including a foil inductor) and Altec Lansing 811B horns as midrange tweeters. I'm planning on using better speakers and putting two speakers in each cabinet like in the article. The crossover network needs to see an 8 ohm woofer, so I can hook up two 4 ohm woofers in series or two 16 ohm woofers in parallel to get the equivalent 8 ohms. Which would be better (lower distortion, transient response, etc.) series or parallel assuming equivalent speaker specs except for impedance? I found one thread here: Series-Parallel Or Parallel-Series
FullRangeMan says: "The best sound quality connection is parallel by a mile" in one post and shaan says: "the series connection provides better transient response" in another post.

The first picture below shows the horn design in the article and the other two pictures are of my horn system.