I can't comment on the metalurgy/frame building aspects of this thread but here is my specific experience .

-- I have a 2004 Cannondale CAAD7 (Alu) frame with Shimano 105 and Ultegra components/Mavic rims on Shimano hubs. Was $1350 new in 2004 (MSRP was 1500)

-- I had a 2005 Jamis Quest Steel (Reynolds 631) frame with pretty much identical components about $1250 new. That frame has since been replaced (car accident) with SOMA frame of similar construction (Tange prestige tubes). Other than Jamis and boutique frame sellers like SOMA and Surly, there aren't a lot of midlevel steel bikes out there.

-- Defer to frame experts out there whether one can make qualitative comparison between CAAD7 and reynolds/tange steel tubes

Cannondale is definitely stiffer and about 1.5 pounds lighter (18.5 versus 20 -- I am a clydesdale so 1.5 pounds give or take is not an issue-- if only I could get the saddle lighter). I notice benefit of stiffness mostly in acceleration or mashing on pedals going up hills.

Jamis/Soma is definitely a bit smoother. I notice this mostly when cruising along on flats.

When riding steel bike in aggressive group rides involving hills and accelerations, I have work a bit harder than when on the Cannondale, so end up more tired at the end of a ride. But on long moderately paced rides, I feel better at the end because of the plusher ride of the steel bike.

I love both bikes and choose the one I ride based on how I am planning to ride that day.