What kind of needles do you use? I have a whole collection of different types made of different materials. My current favourites are metal Addi turbos because they are so smooth and light. But I also have bamboo (Takumi) and resin sets (Denise interchangeables, sadly missing one 5mm tip) which I also use from time to time.
The only type of needles I never use are aluminium, because my yarn always slips off and they make a terrible sound when they rub together.
I noticed a subtle difference in the knitted fabric I got from various needles, but never really paid a lot of attention to it. Until now.
Alexis also wrote a post on circular vs. flat swatches, which is also very helpful. And super interesting. You should read it.