Spendor D7 vs. Harbeth Super HL5+

It is hugely subjective. 
One’s system is just that: a system with different components. Then there is the room which is a vital factor. How loud do enjoy your music? One steady volume is much easier than using a wide range. Some speakers/systems sound great at 80 dbls but sound pale at low volumes. Then there is the music: some recordings will just sound bad on certain systems and speakers.

Only you can figure this out at home...

Seriously, as someone who has demo’d over 20 speakers before choosing D7’s, the Be speakers rank in the top 10-15% of forward-sounding speakers. The classic Spendor ( non-D series) rank in the bottom 10-30% of forward sounding speakers.

Spendor D series with LPZ ranks in the middle 20% (40-60). They are neutral, not bright.

I would agree with this completely. The A7's are far brighter than the D7.2's.
I'll also add that I've heard the Harbeths and Spendors. The Harbeths do have a warm midrange; however, they are also very laid back. The D7.2 are very quick, very precise, very detailed, and have a superior low end.
The D7.2's are also less picky with placement. In fact, one of the most forgiving speakers I've owned.
Different people prefer different speakers, and different speakers sound different in different rooms. I would try to demo both in your home.
For me, though, the D7.2's were the better of the two, so I went with them.

once again, try the grilles off of your harbeths if you have not.  totally different sound, dynamics, top end and transparency open up quite well.

I heard D9 on Montreal Audio Fest with Chord amplifiers.
The sound was horrible, scratchy, bright, unmusical.
People entered into this room and nobody can stay there more than 2 minutes!!!
But I am curious - was it because amplifier or it is a normal sound of these speakers?

Your description is as far from the reality of the D9s in my system as possible.  They are extremely musical with beautiful clarity and detail.  Setup and proper positioning are paramount to their performance as is true for any speaker with their capability. I can imagine the best placement in a hotel room at a show could be sub-optimal as I have experienced at many shows with other highly reviewed speakers and systems.