I am planning on comparing BTT site possibilities a bit more in my free time, but I thought I would start with a kind of interesting post about this.
Of all of the metros in the Big Ten footprint, these are the "major metros" that have at least a very significant suburban population within a Big Ten state, with the exception of Louisville, KY-IN due to it literally having a major college team located in that city and an SEC school that takes up the vast majority of the remaining fan base (in order of population):
New York, NY-NJ-PA: 20.14 million
Chicago, IL-IN-WI: 9.62 million
Washington, DC-MD-VA-WV: 6.39 million
Philadelphia, PA-NJ: 6.25 million
Detroit, MI: 4.39 million
Minneapolis, MN-WI: 3.69 million
Baltimore, MD: 2.84 million
St. Louis, MO-IL: 2.82 million
Pittsburgh, PA-WV: 2.37 million
Cincinnati, OH-IN: 2.26 million
Columbus, OH: 2.14 million
Indianapolis, IN: 2.11 million
Cleveland, OH: 2.09 million
Milwaukee, WI: 1.57 million
Omaha, NE-IA: 967,604
Des Moines, IA: 709,466
Given their outlier status geographically and significantly smaller populations, I would argue Omaha and Des Moines get the axe right away, lol. Next, I used LinkedIn profiles to look at which of the remaining metros had the most Big Ten alumni (note, not everyone has a LinkedIn profile, so these numbers would obviously be bigger in reality ... but it's a nice estimate):
Chicago, IL-IN-WI: 371,557
New York, NY-NJ-PA: 351,053
Minneapolis, MN-WI: 237,022
Washington, DC-MD-VA-WV: 229,729
Detroit, MI: 213,548
Columbus, OH: 160,108
Philadelphia, PA-NJ: 145,311
Indianapolis, IN: 111,854
Baltimore, MD: 71,203
Pittsburgh, PA-WV: 50,613
Milwaukee, WI: 45,378
Cleveland, OH: 44,412
Cincinnati, OH-IN: 35,982
St. Louis, MO-IL: 25,206
Given the low Big Ten alumni, the fact that 30% come from Illinois alone and its association with the MVC ... St. Louis gets the boot, as well. Additionally, I think Cincinnati should be eliminated, given OSU contributes 44% of the B1G alumni, it doesn't have a GREAT arena and it is definitely going to soon be a Big XII city, IMO, with Cincinnati joining. So, next I wanted to see which metros only had a lot of B1G alumni due to one school. These metros were totally dominated by one school (at least 65%), and thus strictly from an "alumni perspective," they are eliminated from my ideal locations:
Columbus, OH: 91% Ohio State, leaving 15,047 for the other 13 schools
Minneapolis, MN-WI: 78% Minnesota, leaving 52,445 for the other 13 schools
Pittsburgh, PA-WV: 73% Penn State, leaving 13,576 for the other 13 schools
Baltimore, MD: 67% Maryland, leaving 57,837 for the other 13 schools
Even though it didn't make the cutoff of 65%, I also see Philadelphia (60% PSU) as problematic, given PSU fans are incredibly apathetic about basketball, it seems. Additionally, even though Milwaukee is within a short driving distance for a massive concentration of Illinois fans and a decent enough drive for the Michigan schools, its 64% concentration of Wisconsin alumni is giving it the boot for the most ideal locations. Cleveland also gets the boot for being 63% OSU, not that central and not that easy for air travel. So, that leaves us with Chicago, Indianapolis, New York, DC and Detroit. As you begin to dissect these options, it is easy to see why the BTT has been hosted where it has over the years ... these are in opposite/"count down" order of how much I think they make sense:
Detroit: In many ways, Detroit actually seems like an underrated contender. It has almost 213k Big Ten alumni, with two schools (Michigan at 99,381 and MSU at 88,591) having massive alumni bases, not to mention passionate fan bases that would show up. It's a large metro area with plenty of direct flights, and it has a great arena for hosting. However, no other school has more than 3,000 alumni besides OSU (3,878), and it is a pretty long drive for all other fan bases besides MAYBE Indiana/Purdue fans living in Northern Indiana. Additionally, while I am sure it is improving ... Downtown Detroit frankly does not hold a candle to its most similar competitor here, Indianapolis.
Washington, DC: While many will think of this as a less-than-ideal location, DC actually has a ton of Big Ten alumni ... 56% are from Maryland, but there are still 11 Big Ten schools with over 5,000, and 2 others (Michigan at 12,252 and PSU at 26,989) with over 10,000. Additionally, many see DC as far more of a "destination" than Detroit, and flights would be easy. The main problem I see here is that attendance might hinge too heavily on how good Maryland is, as a lot of the classically passionate Big Ten basketball fan bases are in the Midwest and either (A) do not have that many alumni in the metro or (B) force their fans to pay for an expensive trip.
New York: I know people got upset about the BTT in the Big Apple, but as someone who went to NYC for the first time last fall and stayed in Chelsea (i.e., not far from MSG) ... come on, this is a great host site occasionally. NYC is the biggest destination in Big Ten Country, it is extremely easy to travel to, it provides incredible exposure in an iconic arena and it has a TON of Big Ten alumni. On that last note, 12 Big Ten schools have at least 5,000 alumni, 9 schools have at least 10,000 and 4 schools have over 20,000. Rutgers' newly energized fan base (157,458 alumni in the area) would definitely show up, but even if they lost early ... you have 28,269 Michigan grads, 24,371 from Maryland, 14,992 from Wisconsin, 13,145 from Indiana, etc. I wouldn't want NYC to be the location TOO often, but if this thing is going to rotate outside of the traditional two sites of Chicago and Indy ... this is the most logical spot.
Chicago: Every fiber of my being wants to put Chicago at #1, but the area around the UC just simply isn't great ... and that's the ONLY thing holding Chicago back. Chicago has over 370,000 Big Ten alumni, and 7 schools have over 15,000. Even if Illinois loses early (and its 118,349 alumni in the area stay away), you have basketball-crazy fan bases ready to gobble up those tickets - Purdue at 38,207, Indiana at 35,539, Wisconsin at 28,168, Iowa at 25,652, MSU at 19,659, Michigan at 19,901, etc. On top of that, it is an incredibly easy drive for fan bases of Wisconsin, Purdue, Indiana, MSU, Michigan and Iowa, and Chicago is one of the easiest flights to book in the nation. The ONLY reason Indy will finish ahead here is the absolutely amazing job the city has done with its downtown.
Indianapolis: This is, sadly, the best spot for the BTT. While it has fewer Big Ten alumni than Chicago, NYC, Minneapolis, DC, Detroit, Columbus and Philadelphia, it has a lot for its relatively small size, and it truly embraces the event unlike the other cities listed above. Indiana (54,017) and Purdue (44,738) are the only schools with sizable alumni bases in the area, but it is a super easy drive for Illinois fans, OSU fans, MSU fans and Michigan fans. Again, though, the real selling point for Indy is its ability AS A HOST and the niceness of Downtown Indianapolis - things that are hard to quantify. The one caveat for Indianapolis is that attendance will likely hinge on Indiana, Illinois and Purdue being good/still in the tournament.
In summary, if you don't want to read all of my rambling, the BTT should really rotate between Chicago, Indy and an East Coast location, IMO; with our additions out east, the latter seems only fair, not to mention a great marketing opportunity. However, considering you can drive from DC to NYC in about the same time it takes to get from Iowa City to Chicago ... I would say axe DC and make Madison Square Garden the only location out there. If it were up to me, the sites would go like this:
2021-22: Indianapolis
2022-23: Chicago
2023-24: New York
2024-25: Indianapolis
2025-26: Chicago
2026-27: New York
And repeat.