CoH2 "classic", I'd play it. It's things like that that make you wonder. if every faction was released as it was and balance was never touched, would everything be balanced because everything is OP?
The newer factions wouldn't be able to compete with release Soviets/OH, specially if we consider their release state DLC commanders.
OKW: even for how broken this faction was, they don't have the tools to deal with clowncars or even worse, original maxim spam combined with crushing T70. It would be trivial facing them using Soviet Industry or HTD PPSH.
UKF: is in a similar position to OKW, that they only shined at late game (remember they sucked hard on 1v1). They will probable get over run by release Osttruppen/Assault Grenadier commander with FHT hitting the field soon after.
USF: if they don't face AssG/Osttruppen they should do more than fine, specially with Rifle Company or Greyhound cheese.
What it would be interesting to play is Soviets vs OH and USF vs OKW exclusively.