There's a whole lot of useful discussion in this thread.
why not just apply an eq curve that matches the mk4v to the ck61 capsule you already own?
That may go some way toward the "similarity" concern but no amount of eq will really match different mics. There are aspects of the sound of mics that don't show up in spec sheets/frequency plots (as dsatz starts to discuss above). I perceive or label those differences as "tone" and "soundstage" (some may group them as "signature") though it involves many different more specific aspects (a lot of which I'm sure I can't explain though I hear the accrual of their impacts). Applying an eq curve to the results of a $20 or $200 mic isn't going to make it match a much better one. Even applying a curve to several different very expensive mics won't make them completely match each other. Of course not all can hear or appreciate the subtleties (see the comment elsewhere by an experienced taper who can't hear a difference between MP3 and wav).
On the EQ topic (which was well covered elsewhere) I will again say I EQ when I feel something needs it but more often just leave them as they recorded because I'm fortunate to be able to run them in really good settings most of the time. The caveat is that I tend to record acoustic unamplified jazz at essentially stage lip position. An accurate mic captures what things sounded like and that's usually great, so I don't want to mess with it. If you record anything that's going through a PA or from further back in a room (or both), each of those factors tends to necessitate some eq for correction of conditions that are adding to or changing the natural sound.
Beyond the natural tone there's also a spatial referencing that may be even more unique Though I'm recording with cards essentially right on the source the recordings have an amazing sense of the soundstage with very precise locational imaging. When you play them you hear exactly where each instrument was on the stage and in reference to each other. I recently did a three horn thing where the mics were centered and it has a surround field thing with a perfect left/center/right (from a pair of cards at less than a foot from the "center" instrument). The depth and imaging is really great and something I don't get from other mics.
I've got lots of examples of flat untouched recordings from the 4V's, but I don't think you're really on the fence about what the mics are capable of. They are the very best stuff I've recorded in over 30 years of attempts. They always sound far better than what I heard in the room even before any adjustments and I rarely do anything other than boost the levels in post to maximize the output/eliminate the cushion required in the live setting.
If your mics require a lot of eq and the same sort of eq every time to get things the way you want to hear them then I'd suggest you're not using mics that are right for what you want to hear.
You didn't say what or how you tend to record. IME the 4V's are best (in a relative sense) at some distance (I mean that IMO you'll notice the greatest advantage from them relative to another capsule or mic with at least a moderate distance from the stage). That lift and signature really helps to cut through the crap aspects of the sound as you go further back in a room. For instance I came back with what I thought was a truly amazing recording from the nosebleeds (near last row) in a crappy and very echoey mid sized hall (others thought it was the best sounding recording from the tour, even relative to a lot of them recorded right up front in the first couple rows). The mics far exceeded my expectations (as well as what I heard there).
Notice though that I almost never use mine in the setting in which I think they most excel. If you're usually close in good rooms the 4's might be an option you'd like. If you
the 4V's vertical orientation is something I haven't quite reconciled (in terms of hard core very low profile use), though I have used them that way it was a stretch to call that spectacle
but it got things done.
Also if you're looking at Milabs new I'd totally agree with the other commenter who says wait and look for some used 4V's. They don't come up often but you could likely get a used pair for roughly the cost of new Milabs. If your budget is large enough for a used set of 4V's don't even consider anything else especially if you've liked how the V's sound. I often smile that if you have the shift on typing both characters 4V is $V, but occasionally you do get what you pay for. They're worth every penny, especially if you can find a nice used pair.