Had a test run on a Genesis equilibrium disc which is as near in spec to the pinnacle Arkose R2 I ended up buying as it's possible to get. The Genesis was steel and twice the price of the aluminium pinnacle but I preferred the pinnacle with it's internal cable routing (even down the chain stays ) . The ride comfort was very similar, in fact I would say if anything the pinnacle was better and a slightly lighter bike.
I'd agree ; ) but the steel bike has a more premium image, sells at a higher price and it's all materials history/rep/sales value. The Equilibrium is quite a stiff steel bike, but not as stiff as many Al and carbon bikes on the market at the time it was conceived. The Arkose, in particular the new frame R and D series, I'd say is a fairly flexible and forgiving Al frame. Not quite as stiff as an Equilibrium overall imo/ime and argualbly more comfortable (for ref I designed the V1 and V2 Equilbriums for Genesis and the Arkose range for Pinnacle/Evans so I know them well. I still own and ride a 2011-12 Equilibrium with the 520 tubes).
And on that note, reading the debate on planing here with interest - I had a custom classic audax style bike made recently, partly to test out how I get on with slimmer steel tubes for longer rides. Standard OS 8-5-8 tubes, 31.8 DT and 28.6 TT, a more flexible tubeset than I'm used to for a road bike. I'm a relatively strong rider but no Cat 1 sprinter. I enjoy the feeling of climbing in bigger gears out of the saddle, similarly enjoy riding my SS MTB. But I'm more of a steady distance rider generally so the BQ ideas interest me. The main thing I've noticed with this new slimmer-tubed Reynolds frame? I climb for long-ish periods out of the saddle with a low cadence/in larger gears with less leg burn than I'm used to or would think of as normal. It feels more natural on this bike. I'm not going to get scientific about it but I've been climbing that way on this new bike a lot simply as I'm finding it rewarding and complimentary to my riding style.
There is something in the BB flex/sway that feels 'right' when climbing like this. It's not the same as the oval ring I use on my SS but there is a similar smoothing effect of sorts. There's perhaps a small gain in efficiency of effort or output, or maybe it's purely enjoying the springy feel. But getting up a hill at my normal cadence and gear but feeling a little less stressed by it all is interesting. I've read about planing and gone back to it recently, I remembered that they claim a speed gain but not the lowered leg burn (can you have both? I don't think so). While I have a lot of respect for Jan Haine and his work, I can't see that planing is any more than biomechanics that work for some people some of the time. Perhaps it works for me some of the time. Not sure yet, though I can see where the concept comes from now.