Well, I need to fit three bikes in the trunk of our car, sometimes along with luggage. Earlier this year, I had two 16"-wheeled bikes and wanted one more bike so my family could ride the trails around DC. I bought a 20"-wheeled one, but found it difficult to fit all three in the trunk, and impossible with luggage. I am also an internal-hub man, so the next day, I traded the bike for a Piccolo. I am happy with my decision. The Piccolo was mainly for my wife and son, so simplicity and adjustability (down to an 8-year old - the Piccolo has a telescoping seat post and steering tube), were key factors. 16" wheels allow the bikes to sit upright in the trunk. I could probably put at least four of them in there comfortably. BTW, John at Bikes at Vienna was very polite and accommodating with the purchase/trade, and he gave me a good deal on the Piccolo.

Using your numbers, Steve, and assuming hexahedrons, the Piccolo is 59% larger and the Speed 8 is 122% larger by volume compared to the Brompton. These difference are significant, whether size is or is not an issue for you (does size matter?).

If I were buying now, I would seriously consider the Downtube Mini, especially because of its 8-speed internal hub and Wav's positive review. Heck, I am considering it now because one of my folders is an ancient POS that a friend gave me.

I will own a more performance-oriented bike one day, most likely with larger wheels. I'm getting inspired by Wav, Bruce, and others here.

Your point is well-taken, Steve. But there can be other reasons to choose a more compact bike.

-Paul