The difference in "strength" or robustness really comes about from several factors...
The CZ-52 uses a roller locking system that helps absorb and buffer the effects of the 7.62x25.
The CZ-52 was designed specifically around the very hot Czech ammo, which according to Small Arms of the World is loaded to about 20% greater pressure than the Soviet loads.
The Tokarev, being designed around the older Soviet-power round, doesn't have a recoil spring of adequate power to handle extensive shooting with Czech ammo.
I've seen two Toks that have been shot extensively with Czech ammo. Both showed evidence of moderate to severe battering of the frame and slide. These were both produced during WW II, when the Soviets were turning out weapons as quickly as they could. I have no doubt that the quality of the steel wasn't up to either pre or post-war standards.
However, I really think that the Tok would handle the Czech ammo a LOT better if a stronger recoil spring were fitted.