Based on the information provided, I will compare the potency of atorvastatin's HMG CoA reductase inhibition with that of Lipitor.

Atorvastatin is a type of drug known as a statin, which works by inhibiting HMG CoA reductase, an enzyme that plays a crucial role in the production of cholesterol in the body. By inhibiting this enzyme, atorvastatin helps reduce the levels of low-density lipoprotein (LDL), or "bad" cholesterol, and increase the levels of high-density lipoprotein (HDL), or "good" cholesterol, in the blood.

Lipitor is a brand name for atorvastatin, meaning that Lipitor and atorvastatin are the same drug with the same active ingredient. Therefore, the potency of atorvastatin's HMG CoA reductase inhibition is the same as that of Lipitor.

It is important to note that the potency of atorvastatin and Lipitor can vary depending on the dosage and individual patient factors, such as age, weight, and liver function. Additionally, while atorvastatin and Lipitor have the same active ingredient, other factors, such as excipients and manufacturing processes, may differ between the two.

In summary, atorvastatin and Lipitor have the same potency in inhibiting HMG CoA reductase, as they contain the same active ingredient. However, the potency can vary depending on the dosage and individual patient factors.

Sources:

1. [DrugPatentWatch.com - Atorvastatin](https://www.drugpatentwatch.com/drugs/atorvastatin)
2. [Mayo Clinic - Atorvastatin (Oral Route) - Side Effects, Dosage, Interactions - Mayo Clinic](https://www.mayoclinic.org/drugs-supplements/atorvastatin-oral-route/side-effects/drg-20067102?p=1)
3. [MedlinePlus - Atorvastatin](https://medlineplus.gov/druginfo/meds/a601244.html)