Hi, Beth. It depends on contexts.
"夫妻" literally means "a couple". 夫=husband, 妻= wife; For example, "这对夫妻很恩爱。", which means that "This is a loving couple." But I wouldn't use "夫妇" in this sentence. Another example is that “夫妻之间要以礼相待。” I wouldn't use "夫妇" in this sentence either. The second example means that husbands and wives should show respect to each other.
I assume that "夫妇" is less frequently used than "夫妻" in everyday life. I can think of an example, “A和B结为合法夫妇/夫妻。” In this example, both phrases are acceptable. It means that A and B are a married couple protected by laws.
Joyce