This Rochester native is well acquainted with all three airports (tho haven't been to IND since 1993 so info is dated).
US 733s and A320's are very comfortable a/c. The seats on both are plenty wide for my 5'11.5", 190 lb frame, and seat pitch on both is good. The gray and beige interiors are tasteful, and in my experience always kept very clean.
The A320 is 7 inches wider than the 733, and the difference is notable. Seats are slightly wider, and the seatbacks are higher on the A320. The A320 seatback fits perfectly into the small of the back of my head. A320 seatbacks on US also adjoin side-to-side directly, so they offer a little more privacy.
The only disadvantage to the A320, in my view, is its smaller windows. I can still get good photo aiming, but find that aiming is a little easier through the 733's bigger windows.
PIT is one of the best connecting airports in the world, IMO. The concourses are wide and have lots of moving sidewalks. PIT is not congested, due to widely-spaced runways and traffic well below the airport's capacity. It's a very easy airport to get around in, with good signage.
IND is a standard medium-size airport, with four concourses and a two-level terminal with two-level approach road. IND has parallel widely-spaced runways so there should not be any ground delays due to traffic. At rush hour, IND's terminal is probably very crowded; traffic there is strong and there haven't been any substantial building capacity improvements since the late 1980's.
There's an excellent indoor and outdoor observation deck on top of concourse B, where concourse C splits off. Be sure to visit it if you have time. I have a pic at the site taken from this deck:
Click for large version
Photo © James C. Kruggel
If you're from ROC you're probably familiar with our snazzy, easy-to use airport. I just wish Nick Tahou would open a stand in the airport so I could get a garbage plate before leaving town. Of course, garbage plates may have effects that are undesirable at high altitudes. :+)