At 100 yds, they are so close as to be the same. Zeroed at 50 yds, the 17 HMR (17 gr poly tip) will strike 0.3 inches below aim point, the 55 gr .223 will strike 0.5 inches below. However, at ranges over 150, the tiny little .17 HMR starts shedding veocity pretty quickly, and the .223 will be flatter.
Source:Winchester on line ballistic calculator
What we have here is... failure- to communicate.