Hi silkowski,
There is no architectural difference between the provided part numbers. Both of these part numbers are power limited at full threading, and while lower power workloads can run faster on the 7501, it is capped to 170W power tracking. The 7551, on the other hand, allows you to raise the TDP from 180W to 200W, by modifying cTDP in the BIOS, if the OEM designed the system cooling to allow for that TDP. By increasing the TDP on the 7551, it is possible to achieve higher overall performance depending on the workload.
For more information on cTDP, you can browse the following posts:
Re: What is configurable TDP, and what values can I set for my EPYC processor?
Re: Ability to Control Power Consumption?