If I was setting up a SaaS company outside of the US, I'd be concerned with tax rates, acquiring a bank account and processing credit cards.
It is worth noting that you don't necessarily have to have your bank account in the same jurisdiction that the company is incorporated.
There are many zero tax offshore jurisdictions (like BVI and Cayman Islands) and at a large scale you can get bank accounts and process credit cards anywhere. But, starting from zero I think it's a lot easier to use Stripe or Braintree.
I've listed several jurisdictions that are compatible with Stripe and Braintree by corporate tax rates. You may be able to achieve a lower rate by paying yourself a salary.
Stripe & Braintree
Ireland (12.5%)
Singapore (17%)
United States (~35%)
United Kingdom (~20%)
Braintree
Lichtenstein (12.5%)
Isle of Man (0%)
Jersey (0%)
Guernsey (0%)
So, I would consider Ireland and the above Crown dependencies.
Sources:
https://www.braintreepayments.com/country-selection
https://stripe.com/global