@Edward and Jaycel is correct. CURRENT annual income is always king. There is no need to use both income and assets.
Notice what the I-134 instructions say:
"Item Number 18. Assets. Provide information about any assets you will use to support the beneficiary for the anticipated period of his or her stay. List only assets that can be converted into cash within 12 months and that will be used to support the beneficiary while the beneficiary is in the United States. Provide the value of all assets listed in U.S. dollars, regardless of whether they are held in the United States or outside of the United States. Do not include assets from any individuals named in Part 3."
Fun Fact: The I-134 for a K-1 is valid for only 90 days, and is actually not enforceable or legally binding. The I-864, which you submit after marriage, is valid much, much longer, and IS enforceable. Three separate courts have held that the Form I-134 was not enforceable against a sponsor by a state agency seeking to recover the medical costs incurred by the sponsored immigrant.1 The courts held that that affidavit of support does not form a legal contract but represents only a moral obligation.
Having said that, most all consults will require an I-134 to help determine if the visa holder will become a public charge. This is to protect the visa holder and taxpayers.
If current annual income is sufficient, I would skip the assets declaration.