Edit: I ordered the 53cm Rando frameset with a carbon fork and 650b wheels. but this discussion might still be useful to someone.
I'm looking at a Twin Six Standard Rando as an all-rounder bike. I'll likely take it on more rugged singletrack than I should, but nothing that overwhelms the 43-47mm tires. it will spend most of it's time on roads and bike paths, unpaved whenever possible. Here's a chart I captured from bikegeo.net of my current Traitor Crusade cyclocross bike with a 52cm frame, and the way that I could likely make a 53 or 55cm Standard Rando fit about the same way:The current fit I have is as long and low as I would want any bike to fit. I could stand to raise the handlebar and bring it closer to me.

basically, I can make either fit by using a longer or shorter stem and spacer stack. I also plan to put a PF30 eccentric BB adapter on this bike for a singlespeed drivetrain, which will alter the reach and stack by up to 7mm in any direction but down (look up the Wheels Mfg. EBB instructions to see why that's necessary). so the reach, stack, seat tube angle, and rear-center will be affected based on where the cranks end up. in the end, it's less than 1 cm of adjustment, so it's probably not a big deal.

any reason to chose one over the other?