This could be po-tay-toes vs po-tah-toes; but with sweep charging you are using refrigerant to sweep out or push out air & non-condensables from the hi-side to the lo-side and suction service port. The amount of time to accomplish this and assure no non-condensables is a judgement call and then right to charging the spec'd charge. Pulling is using a vacuum pump to pull or pump out to a vacuum, THEN add the charge. Either one can work, but I wouldn't trust sweep charging with today's critical charges and sponging, or some call the blotter method, is compliant if you're in to that.