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