It's just that Stefan is a good commander on top of being able to field large armies, and the Vatatzes will have a lot on their plate that may force them to have to field one or two armies in Sicily or Italy against the Durazzos or Tarantos due to the post-Robertian anarchy we see after his death, and the conquest of the rest of Sicily under Louis the Child would be needed.Why so much Serbian hype? Don't get me wrong they are going to be strong but certainly not undefeatable. I mean Bulgaria and Hungary can be used against the Serbs. Also I have not so much faith in the Wiki army estimates tbh. Serbia could muster a lot of troops but certainly not all of them of the highest quality or experience.
Its just that Serbia would choose the battlefield, especially in the beginning where the Vatatzes would have their focus scattered between different regions that makes the Serbs really hard to fight against.
I do agree that the Lascarids would have a better army in general and a navy which the Serbs don't have.
I think the Lacarids would need to fight against the Venetians bc of many reasons, so I agree with your analysis, especially when the Lascarids are more allied with the Genoese than with the Venetins due to commercial ties, while the Venetians and Lascarids should have less ties commercially, so breaking ties with them would be for the better, especially if they gain Crete and/or Euboea.@galileo-034 very good analysis!
I think it is worth mentioning that the original core of Philanthropenos army was comprised of 3,000 Cretan rebels. I am pretty sure their nobles have gained by now rich fiefs in Sicily, Calabria and Greece. By 1350, it will be their grandsons that hold those fiefs. Yet Cretans have proved that they have long memories. It might be plausible that the heirs of those exiles might agitate the Lascarids towards war with Venice. Or might not.
The prospect of the Venetian-Catalan alliance crushing Genoa will be a grave threat to Sicily, especially if the Lascarids have finally conquered Catalan Sicily. The Catalans are natural enemies of the Genoese over Sardinia. Moreover, Pedro IV conquering Majorca will increase the potential catalan threat.
Then it is the matter that sicilian wheat feeds Genoa and guelf Tuscany, while Genoese and their guelf allies consume most of the (low quality) sicilian cotton.
Overall, there are major stakeholders that would be against the Catalan-Venetian alliance.
Hungary is another major ally that would act against Venice, and I think it'd just work in the Lascarids' favour. If they stayed neutral against Louis of Hungary I am sure they will have a good working relationship in the next few decades.