Just my opinion here,
I have made butter and oil (coconut) both.
Butter makes me gag. Somthing about the butter mixed with weed smell. In brownies I am sure it would be fine, but if used where you can taste and smell it more I am put off by the aroma.
We used to make cannabutter in the crockpot but once I got the Source Turbo I’ve never looked back. Like you I’m on the lookout for that ‘weedy’ taste which is kinda funky. Now our cookies taste just like any other good Tollhouse recipe.
I don’t think it makes any difference to your brownies.
I prefer using coconut oil for brownies, and I try to stick with the Pillsbury brand brownie mixes. Thiers calls for 2/3 of a cup of oil as opposed to 1/2 cup for Betty Crocker and the other big brands I’ve looked at. I figure the extra oil is a good thing.
I have used butter in the past, and they came out fine, but not as good as with oil.
Another note, if you use coconut oil, make sure your eggs are room temperature before mixing. If the eggs are cold, the coconut oil starts to really thicken up making it very difficult to keep mixing, lol.