Planted Tank Obsessed
Join Date: Jan 2015
Location: Newmarket, Ontario, Canada
It would be a hot debate to suggest which of EI or PPS is 'better'. My answer would be that EI is better for your tank if you do the 50% weekly water change. EI ensures your nutrients are never non-limiting.
Since you said that you like to fertilize just what is required, then it sounds like PPS is best for you, and that you should double up on your dosing the day before the weekend if you are worried about running a lean tank for a few days.
The more water changes you do with PPS, the higher you can dose and approach an EI non-limiting condition. (for example I daily dose like PPS, but with concentrations higher than PPS - closer to the lower end of EI, and change 12% water every 2-3 days). I would consider this a hybrid of PPS and EI.
In summary, the amount of water changes is a factor to how you dose. 50% a week allows EI. Very little forces PPS (or PMDD). There is a middle ground where you can dose higher than PPS, but change less water than 50%.