the information I have would suggest that there would indeed be a difference between the two products; my guess is that it would probably involve higher levels of ultrafiltration. Nerl themselves appear not to apply the "ultrapure" name to their reagent grade water.
This makes sense. That Thermo Scientific is packaging Safe & Secure UltraPure as qty 6 1- pint bottles suggests this is water for special needs not requiring larger volumes and those needs are not so great that it is commonly saleable on-line.
As best I can tell, the description for both the 'simple' 9800-5 Reagent Grade Water and the S&SUP read identically, viz.: "ideal for reconstituting chemistry or coagulation products, preparing analytical standards, or rinsing delicate electrodes. Prepared at 18 megohm/cm specific resistance using reverse osmosis, mixed bed deionization, activated carbon filtration and final filtration to 0.2 micron, our water is essentially free from organic and inorganic particulate and soluble contaminants."
Fwiw, the MedicalMailOrder.com folks shipped the 44lb box in less than 24hrs, so that's a good sign. I didn't do the math but I'm gonna guess that at roughly $34 for 5 gallons, its still cheaper than Dasani. :-) And if its as good as the stuff Lloyd sends out then my wallet, my records and Ms. Loricraft will all be happy. I'll clean, listen and letcha know.