Speaker shootout question -- do you position the same or differently, depending?

I set my speakers equal distance from the rear and side walks, then fine tune adjustment with a set-up CD. 

To manage room effects, several methods of speaker placement (such as Cardas) depend almost entirely on the room geometry, without necessarily taking into account a speaker's characteristics.  However,  chances are, a near-flat frequency response isn't your only speaker placement goal. I've used a formula that has been referred to as the "Allison Rule", which also can take into account your speakers' bass response characteristics. 

The rule states that the distances from the woofer (or woofer midpoints) to the floor, woofer to the side wall, and woofer to the front wall should be as different as possible (in order to minimize room effects). To accomplish this, apply the following equation:

Middle distance squared = shortest distance multiplied by longest distance.

The woofer height (H) is fixed (in my case, at about 22 inches). For the distance from the front wall (F) , I choose a distance that that seems to optimize bass response of my speakers, consistent with furniture placement and good imaging/soundstage. So I set F at about 36".  The formula then derives the optimal distance from the side walls (S):  36^2 = 1296;  1296 / 22 = 59".   So my speakers are about 36" in from the front wall and 59" in from the side walls. 

This approach works with your room geometry, but allows you to choose one of the 3 dimensions for good bass response (or for whatever else you're trying to satisfy, such as your spouse's furniture placement preferences).  But the optimal distances for bass response vs. imaging etc. are likely to vary (maybe a lot) from speaker to speaker.  

The OP forgot to mention 1 critical thing in his opening statement that make a big difference and the brought it up later: “But for folks who may have another way of testing both their room and the speaker, e.g., when there is a lack of flexibility in the placement”.

If your speakers have a specific spot that they have to reside in because of lack of space or WAF, then that changes everything and if this is the case for this install, why not bring this up initially? Why would the OP state positioning the speakers optimally if you can’t?

There's no point in positioning the speakers in "roughly" their optimal position - actually, that's an oxymoron. Unless the speakers are radically different in their design, their optimum position might only vary slightly from speaker to speaker since, the major factors of dispersion and bass response apart all the other acoustic variables are remaining the same. I second Riley804's post - position each accurately using tape and listen carefully - with only one pair of speakers in the room at a time.

Put each where they sound best to fairly evaluate and remember that where they fall in your room will be one factor in deciding which to purchase.