I always found Quick Start to be excellent, it is stronger and more effecting the Stress Zyme, its just that no obviously no product is going to be a replacement for cycling the tank but I found Quick Start sped it up and made sure it was more stable. I have always used similar products to see which ones worked best as at one point, I was having to recommend them and Quick Start was my number one product. The only times I found it didn't work was when customers spent too much time reading too many different opinions online and got so confused they ended up half heartedly adding a bit now and then and wondered why it didn't work.
I gave up trying to use science and logic in cycling tanks for the most part because it just made it so complicated and in the end, I personally wasn't getting any better results. I make sure I have a decent test kit (JBL, Salifert, Red Sea.. API but only because I know how to read it and when to ignore its false positive readings). And I fill the tank up with water and dechlorinate etc, add the full dose of QS on the first day and half dose on second and third day, 50% waterchange on day six or seven and adding dechlorinator and full dose of QS followed by two days of half dose and at the end of that week I do another 50% waterchange and add the full dose of QS and add two -three little fish (and do two days half dose after adding fish).
That's just how I do it, I also try and use a bit of mature media from someone when I can but for me, even without... I see a predictable rise in ammonia and as it drops the nitrite spikes and then as that drops the nitrate spikes which is removed by the waterchanges. It is a quick cycle so I don't stock very quickly, just a few fish at a time. Might not work for everyone but I have set up a lot of my own tanks and tanken them down and started again when I got bored and set up tanks for other people and display tanks etc and it never fails me except when I miss steps in which case its my fault or whack too many fish in at the end.
But joys of the internet... you have to make up you own mind! Sorry for rabbiting on! But seeing as you have the product now, I found my way of one day full dose and two days half dose (that might be the instructions I think) but repeated each week for three weeks works the best.