Making a quick comparison between summon monster and Astral Construct at various levels, ignoring feats like Augment Summoning and Boost construct:
- At level 1 the AC beats severely everthing present in the summon monster list; in terms of combat ability, the astral construct is way better than any of the monsters in terms of AC, to hit bonus, damage or hit points. The monsters have some versatility -web spinning, poison- but also does have the construct. At later levels, summon monster I is useful to check or spring traps; the construct still wins, because you can direct it mentally to do exactly what you want without having to communicate directly, and have to spend a meager 1 pp.
-At 2nd level, the fiendish vermin are an option against the astral construct. They are slightly worse in terms of attack bonus or damage, but the scorpion has 3 attacks and improved grab (it only works against small characters, though). Nothing can beat the construct´s durability, though, with 31 hit points and AC 18. IMO, the construct wins, but it´s not a beating as severe as at the previous level.
-At 3rd level, the monster´s star is the celestial bison. It beats the construct in attack bonus and damage, have damage reduction and more hit points. Less armor, though, but it´s the only disadvantage. Given the fact that you can also summon monsters with more attacks and others with interesting special abilities (like the dire weasel or dire bat) I´d say that at this level summon monster wins.
-At 4th level you can customize the astral construct so it beats every monster in the list in terms of attack bonus and damage. Still, you can choose the howler (those quills are dangerous), the fiendish dire wolf for brute force and trip goodness, and monsters with multiple attacks, like the lion or giant eagle. The construct still has better armor and hit points, but almost every monster has damage reduction. Monsters win.
-At 5th level the construct has 2 attacks and reach, making him quite dangerous, but not much more than, say, the celestial brown bear. The monsters have the interesting Achaierai, bearded devil and hound archon, with spell like and special abilities the construct can´t emulate. The construct clearly wins in terms of damage dealing, specially taking the extra attack special ability, but still it doesn´t have damage reduction (on it´s own, it´s true that it appears in the Menu B list) but the mosters have a slight edge on flexibility, specially when they can summon 1d3 or 1d4+1 monsters with real combat ability.
-At 6th level the champions of brute strenght are the large earth elemental, the celestial polar bear, celestial dire lion, and fiendish constrictor snake. All of them are clearly inferior to a construct with the improved grab option. The construct also gets DR 10/magic, making it really tough to kill. The monsters redeem slightly having monsters with more varied DRs and tricks like the air elemntal´s whirlwind. But if you want to severely beat an enemy, choose the construct.
-Level 7: Whoa. This level has the mighty Huge earth elemental, and even the construct has to admit that 2 slams with +20 (1d8+12) are worse than 2 slams +19 (2d10+9). The elemental even has 50% more hit points and a higher quality DR, good feats for laying waste on enemies, and better reach. The construct is, however, armed with the mighty menu C abilities, and has a lot of flexibility on top of being a combat monster (wich can make him even a better combat monster), but again the monsters have things like the avoral (spells and healing) bone devil (ice wall at will) and again the air elemental´s whirlwind. Also, in terms of pure damage, the fire elemental is also a very valid option.
- Level 8: Again, it´s like watching the Hulk and the Thing wrestling to decide who´s stronger, but this time the astral construct beats the greater earth elemental in terms of brute strenght when using the menu options to increase his damage output. Both are very difficult to kill, enough to distract a powerful foe for (at the very least) a couple rounds. Other monsters,like the lillend and hellcat, are seriously underpowered for the list, and one wonders what are they doing here except taking valuable space. Still, the monsters still have a couple of spellcasting things, but they don´strike me as so useful.
-Level 9: You get the idea, it´s almosta repetition of the previous level. The elder earth elemental still inferior to the construct, but not so much. Menu C options good. Construct smash. Some monsters with minor spellcasting, but till better than the spell-like abilitoes in the construct´s menu, that limits to blasting. Special mention to the leonal´s heal, though it only heals 100 hit points. There are several monsters with good abilities with Fort saves, like the colossal fiendish spider venom (2d8 strenght damage) or the hezrou´s stench, that could be of use againts an spellcaster.
Generally, the constructs are better at combat, but monsters have a little more flexibility to play other roles in combat other than meat shield and damage daler. Though, being sincere, what one wants in a summoned monster is a meat shield and a damage dealer.
Also, if we introduce feats, constructs are the ones that benefit the most, mostly by the overchannel/talented combo, simply because thay can pull more advanced constructs one, two or three levels earlier than wizards of the same level.
The elemental may be able to take damage...but the A-C is never gonna be hit, even by the elemental! And the A-C will do substantially more damage than the elemental!!! And the A-C can trip on each attack it makes, as a free action...... And the A-C can move where ever its needed, in an instant, and still get a trip attack in.
