the pros/cons all depend on where the player is in their development and what type of school they want attend/play for.
clearly - USHL has the monopoly on the D1 track, as 90%+ of those players usually go onto D1 programs. It's a tough league though in terms of competition, and I would caution players/families who have big egos and high expectations.
Plenty of good players have gone there, lasted a month, and resorted to going elsewhere for an easier path.
BCHL and NAHL provide that softer landing spot in different ways. BCHL is a higher-paced league that has done a great job lately of pushing kids to next level, including D1 NCAA and even pro opportunities. It's certainly a more "fun" league and way less structured than USHL in terms of style of play. So if you're a FWD or offensive D-man, it might be a great option - both as a lead up to commitment, and for committed players, it's a pathway that most schools will support.
NAHL too but not as much - as it continues to become an older/heavier league. Still opportunities there as well, but not quite the yellow b**** road to D1.
In both the tier-2 leagues, I'd advise to pay attention to the standings, and find teams that are notorious for player development. There are several in each league that seem to do it better than the rest on an annual basis. Your advisors/prep/Midget coaches should have some insight into that and/or relationships that could help.