I just need to clarify some stuff going around. DIscussing if VT-4 is better or worse than T-90MS is not entirely related as to which one has the advantage in a frontal combat.
In that respect, i would say that while T-90MS can resist frontally any APFSDS offered by the chinese, the russians DON'T OFFER Svinets 1-2 for export either (these can penetrate 700 and 600mm at 2km according to NIMI and can defeat ERA, making them equivalents to most of the newest western APFSDS, M829A3, DM53/63, etc.). The best APFSDS the russians are offering is Lekalo/Mango-M which like Svinets has special features to defeat 2nd gen ERA (Kontakt 5, FY-II) but has inferior penetration capabilities, being limited to less than 600mm (580mm to be precise, according to NIMI export catalogues) at 2km. While we don´t know the effectiveness of VT-4 base armor, i would be VERY surprised if it wasn't in the 600-700 range, without accounting for the ERA. So, while Lekalo/Mango-M can defeat the FY-II ERA featured in VT-4 sold to countries other than Pakistan, it most likely still won't be enough to completely defeat frontally the tank. If we are talking about the latest VT-4 as offered to Pakistan, the odds are even more in favor of this tank, as it features FY-IV ERA, which is classified as a 3rd gen type, just like Relikt and Duplet (however it is stated by the chinese to be a little less effective than these). Being a 3rd gen ERA (having a "double acting mechanism") it may be able to overcome all the APFSDS mentioned until now, which have capabilities to defeat the previous generation of ERA. This should answer the question as to which tank may have frontal overmatch: basically, no one as none of them are sold with projectiles capable of defeating the other.
Now about the stuff that makes also a difference in combat, who sees and shoots first. Both tanks have thermal sights and CITV, which makes them pretty comparable. T-90MS has 3rd gen thermal sight for the commander and 2nd gen for the gunner (with digital enhancer). I don't know about the specific capabilities of the sights of VT-4 but i would expect 2nd gen for commander and gunner at the very minimum and perhaps even 3rd gen for both. So, again very comparable.
Now, comparing other attributes of the tanks: VT-4 has much better mobility characteristics. Much more modern and powerful engine/transmission on par with the latest in western service. T-90MS still uses a modernized version of the T-34 engine and its transmission, while reliable and proven, doesn't provide mobility parameters on par with the world standard. On the other hand, T-90MS has much better side protection, as the russians offer a lot of ERA alternatives to be mounted on the sides (the Relikt+2S24 light ERA combo is excellent by nowadays standards) while the chinese don't even mount armor on the hull sides of their tanks. Likewise, the turret armor on VT-4 (again, comparable to T-90MS in effectiveness) covers a narrower frontal arc than the russian competitor. So, in my view overall both tanks are equal in firepower, VT-4 wins mobility and T-90MS wins in protection. The really classified aspects of C4I, networking, communications cannot be compared really but what is most certain is that in these areas T-90MS definitely differs from russian service T-90M.
As side notes, T-90MS has some ergonomic advantages over VT-4. For example, the placement of CITV is optimal as to not interfere with the visibility of the commander´s periscopes, unlike what we´ve seen in chinese tanks (and most western tanks as well). Likewise, the integration of the RCWS in T-90M/MS into the CITV is the best solution as to keep good visibility both from the periscopes and the CITV itself, any other tank in the world which has RCWS it ends up obstructing the field of vision one way or the other. Also, the internal arrangement of the commander´s station is excellent, very spacious, ergonomic and well laid out. So, a lot of kudos to the russians in that respect. Oh and T-90MS has air conditioner for the crew, so that's a definite advantage over other tanks. If only the russians had developed a modern engine/transmission for the tank...
