Side by side comparison. Both started the same time, in #6 pots, were in preflower when repotted. The felt pot plant began vegging like mad with a huge growth spurt, while the plastic pot plant continued into full flower.
Same strain, sprouted same day. Yield - plastic 8.5oz, felt 8oz. But they're autos started in the final pot. I use the same pots every grow and have not noticed a significant difference.
If they're the same strain from seed it still isn't a fair comparison, they aren't the same plant. This is why clones are better for experiments. If anything, you showed the variety in that population. Cool shit
These are not clones, but they were the same size in #6 pots. One went into the ole 5 gallon bucket and the other into a 5 gallon felt pot. Both were showing preflowers. The one in plastic just continued straight on into full flower but the one in felt went into a huge burst of vegging for weeks and weeks more, and now it's into flower. Same soil, same cultivar. Make your own decision.
Yeah, if you're serious you want to test one thing at a time to be most accurate, and limit variables. In an experiment, say one where you want to test the growth rate of a plant (dependent variable) in either felt or plastic pots (independent variable), you want everything between the two groups to be the same (environment, media, light schedule, water, feed) except for the pots. This way you will know what caused the effect.
I'm not using clay or plastic anymore. The difference is just too convincing. Ideally I want to buy some 7 gallon fabric pots.
To be fair even the plastic pot is an air pot so its not quite the comparison of say 5 gallon plastic bucket to a 5 gallon fabric.