How much have the monsters changed in the 2025 Monster Manual? Well, one way of showing this is to make side-by-side comparisons of the 2025 monsters to their 2014 equivalents. First up, the Aarakocra.
The 2014 Aarakocra entry had a single statblock for a CR 1/4 creature. There are two statblocks in the 2025 Monster Manual, a CR 4 Aarakocra Aeromancer and a CR 1/4 Aarakocra Skirmisher. Per the Monster Manual's conversion guide, the Aarakocra Skirmisher is the equivalent to the 2014 Aarakocra. The lore entry is significantly reduced - it's only 68 words and notes that Aarakocra "soar the sky of countless worlds" in addition to the Elemental Plane of Air. One additional note - aarakocra often resemble the avians in the world they live in, with the traditional hawk/condor look mentioned alongside hummingbirds and archaeopteryxes. This isn't a lore change per se, but the artwork features a bright pink-feathered aarakocra alongside a hawk.
Also, aarakocra are now classified as elementals instead of humanoids.
As for the stats themselves, the 2025 Aarakocra Skirmisher's AC remains the same, but its hit points have been reduced to 11 (or 2D8+2). Constitution ability score increased by 2, which gives the Aarakocra Skirmisher a +1 to Constitution saving throws, but no other changes to ability scores or saving throws.
The Aarakocra's Dive Attack feature from the 2014 statblock (which adds a D6 to damage if the Aarakocra is flying and dives 30+ feet towards a target) was incorporated into the Skirmisher's base Talon attack with a more straightforward trigger. The Talon attack has the same attack bonus, reach, and base damage, but it now deals 2D4 extra damage if the aarakocra moves 30+ feet in a straight line toward the target directly before making the attack. The aarakocra's javelin attack is now a Wind Javelin. It has the same attack bonus, reach, and range. However, it now deals an extra 2 (1d4) Thunder damage in addition to its base 5 (1D6+2) Piercing damage. Additionally, the Wind Javelin magically returns to the Aarakocra's hand whether it hit or misses after making a ranged attack.