At least they are in the same size range.
map out what are the requirements. Geometry musts. Tire size preferences. Assuming 700c or tubulars.
Who will be doing the assembly?
in general, a complete bike will be less expensive. Purchase, adjust to fit as needed, adapt to it and note how the handling differs from what you otherwise have or recall.
a whole bike will provide answers quickly, then move to the next with some basis of comparison.