Spendor Classics are generally warmer than Harbeth IME. Stirling Broadcast LS3/6s and SB-88s mostly split the difference between the other two (assuming like for like model/size comparisons).
It’s also been my experience that Spendors can handle substantially more power and SPL before they begin to strain, again, when comparing similarly sized models.
Some of the current Grahams and Stirlings, and earlier Spendors (90s) were designed by Derek Hughes. His designs tend to sound better than those of Alan Shaw IMO.