Well of course it will always come down to your own taste.
But I owned the Harbeth SuperHL5plus and I auditioned twice the Spendor D7.
I loved the Harbeths, so tonally believable, rich, incredible with voices etc. But I ended up going another direction and sold them. I’d still love to own a pair though, in a second system. (I use Thiel 2.7 speakers and Joseph Audio Perspective speakers for my main system).
I also own some old Spendors s3/5s that I adore for their organic quality especially with vocals. I thought I should try one of the newer Spendorsto see how they’d updated the sound, hoping they kept at least some of the Spendor midrange magic character.
My experience was that I found the Spendor D7s one of the least appealing speakers I auditioned (and I auditioned many!). They sounded very competent through most of the audio band, well designed.But for one thing I heard nothing like the Spendor sound in the midrange.It was just another modern, clean sounding (and anti-septic) speaker that didn’t distinguish itself in any particular way. (Unlike the Harbeths that just stop me in my tracks whenever I hear them at a store)..
The other thing was the highs were somewhat bright, steely and hard. (Yes they were broken in). I kept trying to turn up the Spendors to enjoy some life and dynamics in the sound (not even that loud) but I was continually having to turn them down due to the hard and piercing high frequencies. I later found out many people had similar impressions of the Spendor D series speakers. They were one of the easier ones to mark off my list.
Again, they sounded really good in most ways. Just nothing at all distinctive or amazing or seductive, and the edge pushed me away.
So, that’s one more bit of data for you from someone who’s heard both speakers.
(BTW, the Harbeths are not rolled off or just soft either. They are very open and lively. It’s one reason why some fans of older Spendor classic speakers find the Harbeth sound a bit "too" lively for their tastes. But I think it’s a canny balance that helps their realism - but not "bright" to my ears).