I know there's all sorts of controversy out there regarding the different brands, with "underdosed" and "bunk" tossed around a lot.
I've never seen a lab of any Moda brand showing its underdosed.
I think it comes down to two factors.
First, Modafinil is subtle. I describe it as being a psychostimulant without the "physical" stimulation every other stimulant including caffeine induces. I consider this a positive for long term use, but someone expecting an adderall, or even caffeine pill like effect won't feel like they're getting much.
Secondly, the speed at which you reach maximum blood plasma concentration determines the intensity of the effect. This is dependent on the formulation of the tab, the excipient ingredients, and most importantly, the particle size of the active ingredient.
If the particles are too large, not only does it take longer to take effect, the peak is lower, and tapers off more quickly. So despite all of the brands having 200mg of modafinil, actual bioavailability varies widely. The difference could be as much as 50% more or less modafinil being absorbed.
A surprising amount of companies make modafinil active ingredients, almost all outside of India, and I suspect suppliers are changed frequently which could explain some batch variation.
I find Modalert most consistent. Sun is part of a serious pharma conglomerate and has the manufacturing capability and expertise others don't, with HAB, makers of Artvigil (a very good Armodafinil, and 2 brands of Moda, Modvigil as well as Modawake), in second place.
I go into the particle issue here: