For scaling, both scale well obviously. They are meant for this. And yo can always covert them to the "Corp" version if you see its worthy (adding more participants, investors, ...)
The selection of either Ltd or LLC depends on many other factors from my POV, just to name some:
For example, if you prefer a US bank account and work with US$, the LLC is obviously the way to go here. If you don't care to much about working with other currencies, then I find Ltd slightly simpler.
If you receive payments from US and you are not from US, and you don't care too much about currency, then Ltd is way better (overseas without taxing).
But if its the other way around (not many US customers, or at least, not the majority), then US is the way to go here.
Personally I don't really care about taxing overseas because I send all my money to my country with an invoice to my local company by the end of the year, hence my earnings in my LLC are virtually 0 (I only use it instrumentally to collect payments).
Both Ltd and LLC will be risky if you spend the money directly from the bank account in things that are not business oriented. So if your intention is avoiding taxes, none of them are the best option (unless there is some sort of country level agreement that don't tax incoming payments overseas, not the case of my country in EU)