There are a lot of factors that should go into that decision...
You can use multiple launch properties to send data into one suite... the largest deciding factor is the underlying code base...
I am a big fan of "single suite" and using segments and Virtual Report suites to separate the content... it's much easier to get overall traffic when it's all in one place (not having to add suites together...) and when it comes to Unique Visitor counts, you can't de-duplicate the users that hit both sites if they are tracked in separate suites... even if they are using the same Experience Cloud ID....
So I would absolutely say yes to a single suite.
But when it comes to Launch... this is where things get tricky... how similar are the code bases? If the code bases are quite different, it can often be easier to separate the tracking code to multiple suites, but when you add, remove, modify the syntax, etc of your dimensions and metrics you will have to update in multiple places...
If the code bases are similar, you can use a single Launch property, but you may make the implementation more complex where you may have to make adjustments based on Site A or Site B (either using code or conditions, etc)....
Without knowing your sites, your implementation structure, etc, this is something only you can decide... either will work.. there is no "right" answer... you will have to weigh the pros and cons of keeping your implementation up to date against both options and make the choice that is best for you to work with.
