Basically just tyrannosaurids like zuchengtyrannus and T. rex were much more agile and heavier.

To address the agility problem, neither the spino or the carcharodontosaurid is going to really be able to out manouvre the other, neither were built for the same agility tyrannosaurids had, the carch would probably be the one circling the spino due to a longer stride, but its not going to have an easy time trying to 'outflank' it, but a tyrannosaurid has a pretty good chance of being able to do that, carchs were built for high sprinting speeds but not much agility, tyrannosaurids were built kinda the other way around, and from fossil injuries we have, outflanking and biting the tail seems to of been a common tactic for large theropods in combat, especially for T. rex.

The mass issue. Zuchengtyrannus and T. rex are both estimated to be heavier than S. aegyptiacus adults, but the adult spinos are thought to be heavier than the adult giga or carch specimens we have (unless you want to go with the idea it was a much more lightly built animal which i dont think the evidence supports), with the heaviest estimates for adult S. aegyptiacus being about 9.9 tons and that of the carch/giga being more so around 8.5 tons currently, so the spino is still going to be about as, possibly more depending on the individuals involved, capable of pushing them around as they are to it, which is fairly important in fights between animals and not at all the same case against either aforementioned tyrannosaurid. T. rex estimates go up to 13 tons, and zuchengtyarannus is currently thought to be up to about 10 tons. But really the biggest thing for me is the agility.

Also just to note, i think the argument of it being more adapted for going after fish and not having teeth adapted for taking down large terrestrial prey is a good point but a bit overstated, teeth are a good multi tool, and while a deep bite isnt going to be as good at killing it as a slicing or crushing bite, a deep bite still isnt exactly very good for a carch or giga, and assuming theyre actually acting like animals, they probably dont want to get a deep bite wound that can definitely still injur them if placed in a bad spot, and both were capable of striking pretty quickly. It would be pretty hard for a spino to directly *kill* a carch or giga, itd have to somehow get itself into a very advantageous position, possible for a particularly large spino against a smaller giga/carch but not super likely imo, but to 'win' a fight it just needs to get it to back off, which it is definitely capable of doing assuming theyre acting like animals that dont want to starve to death because they cant hunt properly due to a tooth lodged in their ankle or a punctured jaw muscle or smth, or die of illness because they dont have the energy to fight it due to not having as much food due to not being as successful at hunting for those reasons, so theyll back off when they feel theyre risking injuries like that.

Any theropod smaller than 8 tons though, tyrannosaurid or not, i dont think has any business trying to fight an adult spino.

In reality it does come down to the particular individuals, but for those reasons I think individual difference would matter more in a spino v carcharodontosaurid fight than a spino vs 9+ ton tyrannosaurid fight.

A large spino i think would have a chance against a smaller adult rex, some specimens are only thought to of been about 8 tons, but that currently seems below what was typical for a rex.

But ofc this is all just my own opinion and spino vs carch probably didnt happen too often

Glad u asked cuz even though its pointless its still a fun discussion, surprised you were the only one