I don't know how I'm going to explain my trip to Evansville to the wife once I-69 is complete.
You mean explain your routing, or your justification for going?
If the former, seems to me that from Columbus, a simple I-70 to I-69 routing would be best (although there were arguments that I-70 to US 41 only added a handful of miles to the trip when people were looking for reasons not to build I-69).
If the latter, me telling my wife, "I want to go drive such-and-such road" is usually answered by, "Have fun and be careful!"
As I noted, nine miles' difference (Google says 19 minutes' travel time difference) between the all-Interstate route and the US-33 > US-50 route. Aside from generally having a speed limit that's 5 mph higher between Columbus and Morgantown (mostly 70 mph versus mostly 65 mph), what's so much better about the Interstate?
That's one of those things that doesn't logically compute if you look at a map. Going basically due east on I-70 and then due south on I-79, vs. a long southeastward angle on US 33, followed by an eastward jaunt on US 50, then more or less due north to slightly northeastward on I-79 to get to the terminus of I-68.
Granted, I've been known to take WV 2, I-77, and US 50 to Clarksburg instead of I-64 and I-79 just for a change of pace, and I will typically default to WV 2 over the interstate between Parkersburg and Huntington, but that's mostly due to roadgeekery interests.