I wonder why the SAA seems to draw more attention and fanfare than open tops. I can't say I've heard of any repro open tops failing. Besides, I think they look cooler, and feel better in the hand.
The 73s are also a stronger design with a solid frame and a screw in barrel instead of being held together by a barrel wedge. They can take a slightly heavier powder load than the open tops. That said, I like the conversions and 71-72s better than 73s in the looks and historical context. 1873 colts are way overrated in TV and movies. They were not that common in the hands of civilians untill the early 1880s. You still saw open tops/conversions in common use into the 90s.
the stronger design of the 73 allows heavier loads, so many shooters prefer them. I prefer the RM converted 1951s and 1860s, myself, but it's all preference.