As Joenobody points out, the lasts really aren't at all similar with the exception of length perhaps. After trying on the Darlton/Marlow wingtips several times, I found that I fit TTS but follow sf guidelines of 1/2 size down in the Barrie. I'm a wide-ish 11 on the brannock and a perfect 10.5 on the barrie. The 10.5 marlow was too snug in the toe box and the 11D fit much better. Not sure if it's available in an E width but my RL store only had the D to try on. I'm now waiting for the next private sale in hopes of buying them. My local RL SA is great about emailing me to notify me about the sales.
I found the Marlow/Darlton to be an "in betweener" size as someone above mentioned. It was a perfect "no fit" solution. They were on a fantastic sale at the time, marked down 40% I believe, but the size problem was a non-starter for me. The sz 8 was too tight, and the 8.5 was too roomy.