I am debating whether I should buy 2 fourplexes or one large apartment building (5+ units).
The loan would either be commercial or residential.
Is it more difficult to get a commercial loan? Are the loan terms (interest rate) for commercial worse?
The loan terms for a commercial loan are not going to be as favorable. You're not going to find a 30 year fixed. It's going to be a higher interest rate, shorter amortization, and will probably have a balloon.