As TR-1 points out the figures for the Soviet missiles were sufficient for the time they entered service.
Also figures for western weapons were greatly exaggerated... look at the inability of Hellfire against Abrams tanks as an example.
It is also important to keep in mind deployment... the best feature of the AT-3 was that it was very widely deployed in enormous numbers.
Tactics would often be used to maximise their effect... for example set up a minefield to create choke points and to force enemy armoured units to skirt around minefields exposes their sides to long range ATGM attack.
Equally in the late 1980s the new top attack sensor fused munitions entered Soviet service on Smerch rockets and later in cluster bombs. In the 1990s these were upgraded to add an IR sensor in addition to the MMW radar sensor to distinguish an operational tank from a flat sided rock or a burning tank.
BTW all the model 2 western missiles were not widely deployed in the 1980s either.
The vast majority of such weapons spent more time hitting point targets at long range like the Milan in the Falklands or the Shturm and Ataka in Afghanistan. For this role all were pretty effective.
Another problem is that soviet tank destroyers and helicopters carried too little ATGMs. For example the MTLB shturm had only 12 missiles while the AMX10 HOT had 18 and all Mi-24s never had more than 4 ATGMs while the AH-1s and AH-64s had 8.
The difference you will find is that every Soviet IFV also had ATGMs, and portable ATGMs were also very widely deployed. The Soviets also tended to deploy more launch platforms, and the Hind could carry 8 missiles and two rocket pods when required with the outer wing pylons wired for two missiles each.
The most important difference was that the Hind was designed to launch its missiles in forward flight where its missiles were command guided and did not trail wires. Western helicopters in comparison tended to launch missiles in the hover which makes them terribly vulnerable to return fire... stationary targets are vastly more vulnerable than moving targets to ground fire.
Did soviet ATGMs have any other advantage other than high speed?
Numbers. Both in deployed systems and also in support weapons like RPG-7.
Weren't the metis-M and kornet 90s weapons?
Metis was a late 1970s weapon... Metis-M1 came later.
And on what helicopters was the Ataka-V used on? As far as I know it was specifically designed for the Mi-28 which didn't enter production until 2006.
ATAKA was displayed with Mi-28A aircraft in the late 1980s... Vikhr was also developed in the late 1980s, though the Ka-50 was kept secret for a few extra years till about 92 or so.