There are 12 illusionist spells of 2nd level in AD&D, the same number as in OD&D. The only difference between the two lists is that dispel illusion is now gone, and has been replaced by ventriloquism. Ventriloquism was a 1st level illusionist spell in OD&D, but now it's been bumped up a level.
Blindness: The target must save vs. spells or be struck blind, permanently. Healing magic won't fix it: only a dispel magic will work, or the caster removing the effect.
The OD&D spell was exactly the same, except that it had a range of 12" as opposed to 3" in AD&D.
Blur: The caster's outline becomes blurry, making him more difficult to hit. The first attack by any foe suffers a -4 penalty, and subsequent attacks are at -2. It also grants a +1 to saving throws against direct magical attacks.
The OD&D spell granted a flat -2 penalty on all attacks, and a +2 bonus to saving throws vs. wands and staves. It had a duration of 4+1d4 rounds, whereas AD&D has one of 3 rounds + 1/level.
Deafness: The spell strikes one target deaf if they fail a saving throw. As with blindness, the spell is permanent and can only be fixed by dispel magic or the caster's dismissal.
Again, the only difference between this and the OD&D version is that the original had a range of 12" and the AD&D version has a range of 6".
Detect Magic: This is the same as the 1st-level cleric/magic-user spell, in that it detects magical radiations within the area of effect. The only difference between the illusionist and magic-user versions is that illusionists cast with a time of 1 segment, as opposed to 2. The cleric spell takes a full round to cast, and has half the range (3", as opposed to 6" for the others). The cleric spell lasts for a full turn, whereas the illusionist and m-u versions last for 2 rounds/level. It also required a holy symbol; the illusionist and m-u spell has no material component.
The only difference from the OD&D spell is that it had a duration of 2 "turns". (Could be rounds or turns. You know, typical OD&D ambiguity.)
Fog Cloud: Creates a billowing cloud of fog that moves away from the caster at a rate of 1". It looks like a cloudkill spell, but it only obscures vision. For practical purposes, it's probably not as good as the 1st-level spell wall of fog, which covers a larger area when cast by a 2nd level+ caster. Other than that, I guess it's used to scare enemies who think it's actually a cloudkill?
The OD&D spell was simply called fog, but it otherwise functioned the same.
Hypnotic Pattern: Creates a pattern of colours in the air. Up to 24 Hit Dice worth of creatures within the 3"x3" area of effect must make a save or become fascinated. Such creatures will stand motionless for as long as the caster concentrates on maintaining the pattern. The material component is a glowing stick of incense or a crystal rod full of phosphorescent material. All told, this is a very useful spell - anything capable of negating a 24HD creature is pretty good, even if it's not all that likely to fail the saving throw.
The OD&D spell had the same effect, but rather than a Hit Dice total it affects a number of targets based on their level: 2-24 1st level types, 3-18 2nd-level types, etc. It tops out with 1-6 5th or 6th-level types. This is a lot less potentially powerful, if you interpret level here to mean Hit Dice. If you interpret it as referring to the levels from the Random Encounter Tables, it's a bit closer to the AD&D spell, but what do you do when its cast against monsters that aren't dungeon dwellers? The OD&D spell lasted for 4-9 rounds after the caster stopped concentrating, whereas in AD&D it stops right away. The OD&D range is 12", as opposed to a range of 0" in AD&D (AD&D covers this with an area of effect instead of a range).
Improved Phantasmal Force: Like phantasmal force, this spell creates an illusory creature or object that can damage anyone who believes it is real. It doesn't require as much concentration to maintain, however, as the caster can move at half speed and still concentrate upon it. It also lasts for 2 rounds after the illusionist stops maintaining it. Most significantly of all, it can now make sounds, though not intelligible speech. The silent nature of phantasmal force is probably the thing that most holds back its believability, so this is a pretty big deal.
The OD&D version of the spell was called improved phantasmal forces, and it gave the caster the ability to move and still maintain the spell. It also continued after the caster ceased concentration, but it lasted for 3 "turns" extra. It didn't say anything about making sounds, but then again the OD&D phantasmal forces didn't specify that it was silent.
Invisibility: Just like the 2nd-level magic-user spell, it turns a character invisible until such time as they wish to reappear or make an attack. The only difference is that it requires no material components.
The only real difference between the OD&D and AD&D versions of this spell is that OD&D gives it a range of 24", while in AD&D it's a touch-based spell.
Magic Mouth: Like the 2nd-level magic-user spell, it allows the caster to endow an object with a magic mouth that can relay a short message. The magic-user and illusionist versions of this spell are identical.
The main difference from the OD&D spell is that it could be triggered based on the alignment of someone nearby, whereas that's expressly forbidden in AD&D.
Mirror Image: This is like the 2nd-lvel magic-user spell, but rather than creating 1-4 images to surround the caster, it creates 1d4+1. It also has a range of 3" per level, as opposed to 2"/level for magic-users.
The OD&D spell didn't grant the illusionist an extra image.
Misdirection: The caster places this spell on a creature or object, and any detection spell cast upon it (such as detect evil or detect snares and pits) will return the wrong information. The caster of the detection spell gets a saving throw to avoid this.
The OD&D spell was called misdetection, which was more literal but also a little awkward. It used the same method as dispel magic to gauge its success, which was determined by the difference in level between the two casters. Using a saving throw is certainly a simpler way to get it done.
Ventriloquism: Like the 1st-level magic-user spell, it allows the caster to make their voice come from somewhere else. The illusionist version increases the maximum range to 9" (vs. 6" for magic-users) and also increases the duration, to 4 rounds + 1/level (vs. 2 rounds + 1/level). Illusionists have a casting time of 2 segment, whereas magic-users could cast it in 1.
The OD&D spell was 1st level for illusionists, but otherwise the same. It had a flat range of 5".