I’ve noticed that some recordings made with Schoeps MK4s, which I’ve downloaded from DIME, tend to sound less wide in stereo but much more centered and upfront—almost “in your face” to my ears—compared with my own MK4 recordings made in a spread configuration. I’ve long suspected that differences in mic placement and configuration could be the reason for this sonic contrast.
That's a good description of what I generally hear from coincident stereo pair arrangements ( X/Y or M/S) verses those that use spacing between the mics. The solid center image and "flatter, in your face-ness" are aspects that make coincident configurations somewhat unique and useful in terms of the sound they achieve, other than the physical mounting aspects. As Goodcooker mentions, X/Y using mics that have a pickup-pattern which features some amount of reverse-polarity rear-lobe will tend to achieve a more "open" and "dimensional" sound, if with somewhat less low bass fullness and extension than cardioids which don't have any rear lobe. X/Y using cardioids may tend to sound somewhat more deep and rich, but often features less depth and sense of dimensional openness. Mid/Side works basically the same, except using a cardioid mid generally equates to a stereo output that is similar to X/Y using supercards, and a supercardioid Mid equates to something more like X/Y using hypercards.
In pursuit of a sound that's sort of a "best of both worlds" combination, it's inclusion of the somewhat unique sonic aspects of a coincident-stereo pair that has influenced my preference for combining a coincident-pair and a spaced-pair when the intent is mixing the two separate stereo pairs together, rather than combining a near-spaced pair and wide-spaced pair which will tend to have somewhat less sonic differentiation between them. That's just my personal preference though, and is not intended to cast shade on the excellent recordings made by tapers combining near and wide-spaced pairs.. nor those making excellent recordings using a single pair.