I wanted to see if there was a difference in drop rates for ichor vs gossamer off spiders using pick vs hatchet and the three different tiers.
I did this in singleplayer using admin spawn commands. I know in other testing threads there were discussions on whether all the spawn in creatures were exactly the same as real in-world spawns. I have no idea, but this was good enough for a quick test for me.
I spawned in 10 green spiders at a time, used the admin kill all command, then harvested bodies. I used 5x harvest rates to test if the 1x you got in default was actually exactly 1.0 or had tenths in it. It seems each gather was exactly 5x so there won't be a difference in vanilla vs higher harvest rates.
I did a second test on longsword and steel hatchet since they were further off than the others. Longsword test 2 was 200 gossamer, 90 ichor. Steel hatchet was 120 gossamer, 120 ichor.
The meat goes up with tier of tool used (stone, iron, steel), everything else was 5x gossamer/ichor per hit.
Personally, my conclusion is it doesn't matter what tool you use or what tier. If anything maybe weapons are better than tools. I know I'm never using higher than stone again and I don't see a substantial difference between pick/hatchet.