Upon rereading –
Well, first I would probably not have this choice, as if I were a D1 athlete concerned about high academics I would have applied to selective D3 schools where my athletic prowess would help get me admitted, and I’d have the best of both worlds, playing my sport at a prestigious institution.
But since that’s not your choice, the answer between the two is very clear: decline the D1, accept the T20. It will hurt to close the doors on your athletic dreams, but attending the best school academically that sets you up for a successful future is clearly the best option. Look at the rest of your life, not just the next four years.
(And you’ve heard the excellent advice – what happens if you get injured and can’t play your sport? Then you are stuck at a mediocre institution AND not playing.)