You do realize that EI is a specific fertilization scheme with substances in different ratios than PPS-Pro right?
EI is not a scheme of dosing ANY fertilizer. It is a scheme for dosing the specific fertilizers specified by the recipe. PPS-Pro contains other compounds as well. You can easily unbalance the aquarium by dosing PPS-Pro per EI.
My two cents.
Ratios make no difference, at all for aquatic plants.
The ONLY thing that makes a difference is when ONE nutrient becomes a limiting growth factor, this is called Liebig's Law of the Minimum.
There's a good reasons why it is an Agricultural plant science law.
The entire ratio business is one of the most abused concepts in algae and aquatic biology.
EI is simply a method to rule out limitations, much like using Hoagland's Modified nutrient solutions for plant research. For aquatic plant water column growth studies, this is typically reduced by 5x(See Geoff 1966). EI simply uses water changes(hardly something I ever came up with) and dosing based on teaspoons rather than making ppm's and mls. Turns out no one needs this supposed balance of ferts, unless they are actually trying to limit growth.
If you wish to limit growth, then use a holistic approach, not just nutrients. Otherwise you end up wasting light and CO2, that's not "balance".
If you want a lower end control, then a pure non nutrient solution using no ferts. Then EI. All other fert dosing routines will fall somewhere between those two ranges.
Now if you have trouble mastering CO2, or have too much light, not enough ferts/CO2, then you will have trouble. In fact, EVERY dosing routine has examples of problems, algae, many other issues, so balance is not due to the dosing method. Likewise, we also find cases where dosing various routines also works well. Obviously, there's a lot more to balance than the mere dosing routine. And the lion share of growth and problems folks encounter in the hobby are light and CO2.
Effort should be placed there, not worrying over the dosing routine.
Now if you want to REALLY evaluate CO2 and light effectively, you would need to make nutrients non limiting, thus independent of other variables.
(this goes back to Liebig's law, but applies now to light and/or CO2)
This teaches aquarist much more and hones their CO2 and light adjustment skills. If you can adjust those 2 parameters, then nutrients are extremely easy and adjustable over a massive range.Why learn to balance just ferts, when you can learn to adjust all 3 factors that define growth rates?
If that was the goal, then PPS is no different than PMDD that came 8 years before and is virtually identical.