Comparing speakers at home questions

When going back and forth I often notice I hear differences best when starting from my one set of speakers, going to the new ones AND especially when going back to the 1st speaker.

@dynamiclinearity  Big +1 on that.  Forgot to mention that earlier.  Switching back to the first speaker is absolutely critical. 

I’ve done both.  I find having both for an ideally a couple of weeks gives me time to listen and get comfortable with the sound and the decision. A more thorough audition than just A/B certain songs and Less buyers remorse.  No better way to buy speakers or equipment in my experience.  

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.