I am, not sure of that. Certainly the Type 055 is going to be larger in displacement, probably 12,000 tons or more versus around 11,000 tons.
The Se Jong have a larger and more robust weapons load.
Their AEGIS system and radars are a well known entity and proven. We simply do not know what the true capabilities of the Chinese systems are. And these will be newer systems still.
Se Jong the Great (KDX-II) Class DDG Armament
1 x 5 inch (127mm/L62) Mk-45 Mod 4 naval gun
1 x 30 mm Goalkeeper CIWS
1 x RAM Block 1 CIWS with 21 SAM missiles
4 x 4 SSM-700K Hae Sung anti-ship missiles (16)
80-cell Mk 41 VLS
48-cell K-VLS
-32 x Hyunmoo III land attack cruise missiles
-16 x K-ASROC Red Shark in (VLS)
2 x 3 K745 LW Blue Shark torpedoes
2 x Super Lynbx or SH-60 Seahawk helicopters
Type 055 DDG Armament
1 x 130mm H/PJ-38 DP mian gun
1 x 30mm Type 1130 CIWS
1 x 64 Cell VLS
1 x 48 Cell VLS
1 x FL-3000N launcher with 24 missiles
(Unknown ASW launchers - may be part of VLS)
2 x Medium Helos
So the Se Jong carriers a total of 165 missiles + 6 more ASW torpedoes, for 171 launched weapons in total. The Type 055 carriers 136 total missiles/launched weapons.
We know that the Se Jong has 16 anti-ship missiles, 32 Cruise missiles, 16 Anti-submarine missiles, 6 ASW torpedoes, and 101 Anti-air missiles. This is a very heavy loadout and very capable all around.
We are not sure what the normal load-out of the 112 VLS will be, though they certainly will include (IMHO) probably numbers of ASMs (both anti-ship and anti-surface possibly) anti-air, and anti-submarine missiles (we believe the ASW missiles will work from the standard VLS cells).
The Type 055 is going to be a very capable vessel...absolutely no doubt about that. I would still rate the Se Jong as stronger overall.
By comparison, the Ticonderoga cruisers carry 128 VLS + 8 ASMs + 6 ASW torpedoes for a total of 136 launched weapons, which happens to be the same number as the Type 055 in terms of the physical number of launched weapons.
Well, obviously 055 will be a meaningfully larger ship than Sejong, at 12,000-13,000 ton full load while Sejong approaches 11,000 tons full load. (12,000 tons is often cited as 055's
standard displacement, rather than full)
We don't know 055's VLS count, but it is expected to be 128. 112 is a lower estimate atm I think.
Sejong of course has 16 additional AShM launchers, while 055 is not expected to have any. In terms of pure missile tubes, Sejong will have a larger number. But the PLAN's VLS also has a much larger diameter than the Mk-41 and K VLS that the Sejong uses. the PLAN's common CCL VLS has 850mm diameter, compared to 638mm for Mk-41. And 055 is built with cold launch in mind as well as hot launch, and with cold launch they can make full use of that 850mm diameter -- in other words, their VLS can fit a much, much bigger missile than Mk-41 will ever be able to. A missile with a bigger diameter means more propellant, larger warhead, larger seeker.
So who wins in armament? I'm not sure, personally. If we're going by the number of missile tubes, Sejong will by a slight margin. If we're going by both number of missile tubes and also the type of missiles that can be fit in in future... then I'd say 055 wins, hands down.
But of course, we all know armament isn't everything. Radar, command and control also matters. In fact in the modern age I think they are the big important toys to consider.
We can say that we don't know how effective those systems are for the PLAN, and that Aegis is a mature system. But we know 055 is a bigger ship than Sejong, so it probably has more space to fit a more extensive command suite. We know they've developed combat systems for 052C and 052D, and 055 will be expected to have even greater command and control abilities. We know 055 will probably have three main sets of phased array radars -- an X band AESA atop their main mast for surface/horizon search, an S band AESA that is the same as the 052D's -- the 346A, a fairly mature system by now. We also expect an aft radar, probably of L band or maybe UHF, for volume search and likely anti stealth roles. That's three sets of powerful phased array radars compared to the single PESA SPY-1 for Sejong.
I think in terms of radar, 055 will also win quite convincingly... once it reaches a similar stage of maturity.
Unfortunately we have no idea how 055's combat system approaches. Aegis is such a mystical standard now, and it has gone through so many iterations, comparing anything with Aegis is simply a difficult prospect.
As for ASW, we expect the full suite of bow, towed, and variable depth sonars. Two 13 ton helicopters are expected, a good 3.8 tons heavier than Sejong's SH-60s helicopters too. That's an extra 3.8 tons of fuel, mission controller and processing systems, sonobuoys, and weapons. We don't know how Z-18F's actual mission avionics and sonar will compare with that of the SH-60s and Super Lynx aboard Sejong, but we can expect it to be at the cutting edge of what the PLAN can offer. But we do know Z-18F will likely have a meaningfully greater payload, and range/endurance compared to SH-60.
So overall, on paper, if one only looked at things like armament count and relied on stereotypes regarding the PLAN's level of development, then one might say Sejong has a clear edge. It has more VLS and missile tubes, it's got Aegis (TM) and SPY-1. But once we consider that 055's VLS is larger and more future proof, and that 055 will have a far more extensive and modern radar suite, and is a larger ship overall with associated more room for command/control facilities and overall growth, then I think it isn't a stretch to say that 055 is quite a few yards ahead of Sejong in this regard.
However it all depends on how the individual subsystems compare. For instance, sure 055 has a bigger VLS, but are its missiles as good on a per volume basis (e.g.: are its propellant per gram as good, are its seekers per area as powerful). Same goes for its command/control, and radar.
So that really depends on what level you believe the PLAN is at for those areas of technology.
If all things in that regard are equal or even near equal, then I'd say the 055 would be clearly superior to Sejong. If not, then it depends how you think things scale out.
Unfortunately we are not compltely solid on the things like VLS count, type of ASW helicopter, or even the actual types of radar used. We'll need to wait for the mock up to be finished, and then the actual ship to be launched before arriving to a final conclusion. But I think the common consensus right now is basically the subsystems I described for 055.
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Edit, I also expect 055 to definitely feature dedicated ASW torpedo launchers of the same type as seen on all PLAN surface combatants.
