Comparing speakers at home questions

I understand the arguments on both sides—short-term vs. long-term listening. I've tried both approaches. However, the key is a blind test.

Best to do both. Big differences can be noticed quickly and are obviously most important 

subtle differences may require more time but are more prone to mistakes. Optimal set up for the speakers will differ and if you don’t get them both set up properly the difference you perceive may result from suboptimal set up, not something inherent in the speaker. Level matching, etc can also be an issue, as can expectation bias. 
As others have suggested, have a set group of songs that you are familiar with to use for the test. I would suggest some that are very well recorded, and some not so well recorded 
 

good luck 

Give thought to the choice of music for comparing speakers. You’ll want to audition speakers using music of the type you favor. Speakers can behave very differently across music types. Differences in speakers can be minimized or seem more notable by the choice of music.

I would echo a previous response about adequate break in of the new speakers. I am assuming they’re brand new and have the time. The sound can change significantly after a 100 hours on them. 
Just my thoughts which are probably meaningless 

@mattldm 

Relax and take it slow, one set of speakers at a time.  Listen for the good and the bad, take notes including what track you are listening to and then after a week or two go to the next pair of speakers. Listen in a relaxed state, take notes again, the good and the bad- and note the track you played.  

F few back and forths should give you a clear picture of which you like the best.