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Uhh the salvo intensity needed to pierce IADS in Ukraine with subsonic missile is *not* an identical condition to what the USN would have to field to do more than land potshots with long distance subsonic salvos from carrier sorties. The longer the transit time for the package the easier it is to intercept. China is not Ukraine and the USN is not Russian land based forces.
There is this notion that subsonic cruise missiles are a kind of 1950s training targets waiting to be shot down just because they lack that .1 mach.
First of all - it is just not the way. Even faster
low altitude cruise missiles don't really fly at mach 3 entire course - you can't fool atmosphere density, you can't fool thermodynamics. As most ASCMs (unlike many LACMs) do in fact cruise at high subsonic speeds at low altitudes - the difference is more around 1.5 times at most.
But it comes with low signature, which can be very low for small objects designed with stealth; note that our whole object exposed projection is comparable/below some LO-optimized wavelengths (052C/D, but also KJ-600!). And stealth itself can be nasty: it's one thing to design reusable bird of prey without any inconsistencies in surface finish (and somehow service it later). It isn't really that hard to design a single use missile this way; think of LRASM. Radar return in targeting bands can be stupid low.
It comes at small size, skimming just over the surface of the sea, in a zone highly inconvenient for bands either way of X-, and X- is the one affected by LO the most (which btw is immediate problem for anything other than perhaps 055 and 054B; in the opposite direction - what a shame that after DBR failure,
no US surface combatants have effective high band radar at all). Ships train a lot against subsonic seaskimmers(in practical rather than electronic shots) not just to write off HHQ-9/SM- missiles, rather because it is an actually demanding task. Nothing magical for a well trained crew, but there is a lot to train, and not that much has to go wrong for a disaster.
Often with simple and effective onboard EW, as (for obvious reasons) there are some very simple and effective ew techniques right over the "screen".
It often comes very dodgy, as same transsonic regime allows small(~PL-15), rigid unmanned craft to perform very radical maneuvers. Especially since modern variants can in fact have onboard RWR.
Last but not the least, it's very easy(and very american) to tightly pack subsonic missiles in very highly concentrated groups, which almost guarantee something will get through. Supersonic weapons....can, but in practice rarely form truly tight packs. Sufficiently smart supersonic missiles till this day are just rarely encountered in such numbers.
Against all that, most supersonic weapons only really have much
shorter engagement window - which is more than offset by their larger profile; and no, we aren't in 1960s, almost all somehow effective interceptors don't have problem leading faster bogey more.
Other than that, their true main advantage (ToT - much better ability to prosecute patchy targeting data) - is Soviet/Russian-specific, it is not
that paramount for PLAN as of 2025.
Supersonic missiles are in most cases much larger, have much larger signatures since take off, can't afford lololo trajectories for safe launches(and their booster ignitions aren't exactly subtle anyway) and in most designs don't overwork themselves hiding launch "spark" anyway(that's Kalibr/YJ-18 btw, speaking of relevance). They don't really give their seekers comparable work conditions.
There is no supersonic ASCM in existence which doesn't have any vulnerability mentioned above - all have some.
Hypersonics are btw even worse from these points - as they don't work at low altitudes at all. Yes, they're truly fast, but that speed comes at a corresponding size and cost.
It is someties ironic on this forum, as more PLAN ships(and aircraft) employ
subsonic, rather than supersonic missiles. I still remember wild dissapointment in 054B thread, when some members were terrified to find YJ-83 instead of YJ-12. When it was objectively a superior weapon choice for China since mid-2010s at the latest, more so for frigate missions in particular. Times when the only ray of hope standing between Fuzhou and 7th fleet carriers were 4 suicidal Sovremenny doing their first and last heroic sacrifice are gone(though ironically older destroyers still carry out this standing homeland guard thing).
When question stands "supersonic or subsonic" - there is no simple answer, and if a navy should choose just one, all things equal, subsonic missiles are better at "one size fits all"(especially since they're often as cheap or cheaper than interceptors), from RIB to supercarrier.
The higher level, the more complicated it gets, but rule of thumb is there are no simple answers even in high end warfare as we understand it.