They are not different. The M103C is what Maco labels its own 3 element Yagi beam.
Sometimes manufacturers use different hardware, or different length sections for their elements with different diameters, and they may use different matching devices as in a Beta match or Gamma match, but thay are all 3 element Yagi beams if they use 3 dipole type elements for the antenna.
Real differences are very subtle, and usually not of consequence.
It is when you change the basics of construction, such as using folded dipoles for the driven element, that room for significant discussion of difference occurs. The spacing between elements can influence how much forward gain, or front to back rejection can be expected within limits, and the boom length can produce some differences to a degree because it offers additional spacing options. There is a limit to what can be expected in difference between any two 3 element Yagi beams.
If you have a manufacturers name for the second Yagi, then those small differences might be discussable.