as a senior D3 runner who is at no name school with awful records that I have the majority of in distance events, I can tell you that I love D3 because most of the athletes are so genuine and it is friendlier atmosphere. There is more competition between teams in D3 than D2 because there are more D3 schools and teams are larger in the D3. There is more poor quality, but the teams are really deep because there are so many athletes that vary in ability in different distances.
My HS teammate is a big shot in DI at a competitive school, all american in XC and 5k outdoors, and the certain pressures/harsh realities have made it very...serious...but, very, very rewarding.
Realize that in DI or D2, especially if you are on scholarship, $$$$ is game changer in more ways that I can tell you. Like, that alone would get its whole thread.
Honestly, D2 is small and there is smaller pool of high quality athletes and less scholarships but the perk is that if you are a high caliber D2 runner, you can get in to big meets to help you pull a PR out of your butt.
as a nationally ranked d3 distance runner, it is hard to find a meet that I know I won't win. PRing comes down to will power against the clock or making odd bets with my coach, like, "if I break X then you have to do the cinnamon challenge."
honestly, PICK A SCHOOL BECAUSE YOU LIKE THE ACADEMIC PROGRAM. running does not last forever. in terms of deciding based on running, PICK A SCHOOL THAT HAS A TEAM YOU WILL HAVE FUN WITH AND A COACH THAT IS NOT A JERK AND WHO CAN HELP YOU IMPROVE.
these things can be found at the DI, DII, or DIII level.
good luck.