The speed will not differ, because the same disks with the same data transfer rate are always inside the external enclosures. The Ultra usually refers more to additional accessories, e.g. rescue software or similar.

A tip from me: the Seagate 5TB disks are cheaper, by the way, and there are always real SATA hard disks in the external enclosures from Seagate, which cannot be guaranteed with WD or other providers. Real SATA disks have the huge advantage that if the external enclosure motherboard in such an enclosure should ever be broken, then you can simply remove the Seagate disk from the external enclosure and read it out on a normal SATA interface.

Here, for example, is an example of a 5TB Seagate drive connected externally via USB 3.0. There is always a Seagate Barracuda 5TB hard drive inside (Seagate does not build hard drives with a direct USB connection):

Seagate Expansion Portable (5 TB)

I cannot fully agree with "Mail".

A data transfer of 315 GB and 60.02. files took 1 hour 53 minutes with the Ultra via USB-C and 1 hour 56 minutes with the "normal" WD My Passport. So the speed is not decisive for the purchase decision.
Interestingly, WD support was unable or unwilling to provide any specific information on this topic when asked in writing.

For me, the WD My Passport Ultra 5 TB is clearly superior to the "normal" WD MY Passport 5 TB in terms of speed. A Timemachine backup of 3.7 TB takes about 20 hours with the Ultra, and 12 days (!) with the "normal" one.
I own two of each and have had the experience described above with all of them.
On the one hand, this may be due to USB 3.2 vs USB 3.0, but that alone cannot account for the entire difference in speed.