I sailed on SC 27's for years.
Express's accelerate faster in less than 4 knots of wind . . . but,
SC27's are faster upwind in less than 10 knots of apparent wind.
SS 27's don't (spinnaker) reach as well with the mast head spinnaker
vis-a-vis an Express . . . and generally rake longer to accelerate.
Downwind SC 27s . . . once there moving are as fast or slightly
faster than an Express 27 in light to moderate 'non-planning'
conditions dead down.
Above 12 knots of true wind express 27's are faster on all points of
sail.
In heavy air there is no comparison . . . Express's are faster and
much more controllable.
For Seattle conditions an Olson 30 is best, SC 27 and then and E27.
MB