Precision 5530 sluggish

This is puzzling me:

I noticed lately (but it may be an older symptom which I only noticed recently) that my Precision 5530 (Intel Core i7-8850H @2.60 GHz - 6 cores) is significantly less responsive than my more recent, but supposedly less capable, MS Surface Pro 7 (Intel Core i7-1065G7 @1.30 GHz - 4 cores).
They both run Win10 Pro, both have the same AV (default MS Defender), both have bitlocker disabled, both have a SSD as system disk, power mode is identical, etc.
On the 'offending' DELL, nothing suspect is reported, and a full OS reinstallation occurred not so long ago.
The symptom is slowish application load, including system features; e.g. clicking on the Windows Start icon, the menu appears instantly on the MS Surface while it takes a noticeable delay, sometimes up to half a second on the Dell. Heavy apps load about 30% faster on the MS Surface. And, except for heavy computing power (e.g. video transcoding) where the DELL performs obviously better, simple productivity apps also work somewhat slower on the DELL than on the MS Surface. Raw disk I/O is as good as expected on the DELL (about 0.5 GB/s on the "old" AHCI system SSD and about 3 GB/s on the newer, NVMe secondary data SSD).
All performance options are enabled in the BIOS (as by default)...and all drivers are up-to-date.
There is no sign of excessive CPU throttling (Task manager)

I wonder if this could have been introduced by a BIOS update at some point: would you recommend resetting the BIOS to all defaults ?

So I have no clue where the bottleneck is (if any): could it be that the i7-1065G7 is so much more 'modern' than the i7-8850H of the DELL that it performs faster for most of the tasks ???