If the difference truly boils down to the rated TDP being 5W higher, than there's no difference.
Most laptops are already using TDPs higher than that. The laptop manufacturer has a high flexibility with the CPUs. I bet it can be set at anywhere from 15W to 25W in 0.5W increments. And that's just the TDP setting. Laptops have more than a dozen different settings(maybe two dozen) related to power/performance.
Forum goers and authors of hardware news still have this idea that manufacturers have to adhere to exact specifications as said in papers. No, dig deeper, and there's far more to that.
Since in practice there's no laptop with the 4800U, maybe it'll just be rebranded?