Hope – Sentinel Crystarium

Character Hope
Role Sentinel
Despite having the lowest HP in the game, Hope makes for a fairly interesting Sentinel. Like Lightning, he doesn't get Challenge and favors Elude over Mediguard and Steelguard, but Hope also gets the counterattack Abilities, Entrench and Vendetta. He's fun to play around with, but not much use against truly powerful enemies.
Compare Hope – Sentinel Crystarium to other Crystariums

Related

Hope

Eidolon Alexander (Chapter 11)
Base HP 170
Maximum HP 18,000
Base Strength 8
Maximum Strength 1,100
Base Magic 20
Maximum Magic 1,900
Starting Weapon Airwing
Primary Roles Ravager, Synergist, Medic
Accessory Crystal Synergist 3
Accessory Crystal Medic 8
Accessory Crystal Ravager 10
ATB Level Crystal Synergist 8
Chapter 1

Fang – Sentinel Crystarium

Character Fang
Role Sentinel
Like Snow, Fang has access to every standard Sentinel Ability (i.e., except Elude), though her lower HP total and relative lack of defensive Weapons makes her a bit less effective than him. She does get Mediguard first, so I guess that's something.

Hope – Commando Crystarium

Character Hope
Role Commando
Hope's biggest disadvantage as a Commando is his low strength stat, but then, he gets Ruin right away so that shouldn't be a big issue. In fact, Commando can be very effective for Hope against enemies that are weak against Magic but resist most Elements. He lacks many auto Abilities, notably including Launch, making him a poor choice as your lone Commando, but then, you're not likely to use him in that Role.

Hope – Medic Crystarium

Character Hope
Role Medic
Hope has access to every Medic Ability, which combined with his high Magic stat makes him the best Medic in the game. He is one of only two Characters (along with Vanille) with access to Curaja, a vital Ability when dealing with powerful multi-target attacks from the game's tougher foes.

Hope – Ravager Crystarium

Character Hope
Role Ravager
Hope is the best Ravager in the game, provided your target is not more vulnerable to Physical than Magic attacks. The only Abilities Hope lacks are the -strike Abilities, which is usually fine but will occasionally make him virtually useless. Hope also has the Last Resort special Ability, which will very rapidly build the chain bonus of a staggered target.

Hope – Saboteur Crystarium

Character Hope
Role Saboteur
Like Sazh, Hope is one of two Characters that can inflict every Status Ailment in the game. However, Hope exclusively gets multi-target versions of these debuffs (as well as the standard Dispel). This makes Hope an effective Saboteur against groups, but since his Abilities cost three times as many ATB segments, he's a liability when you're only looking to debuff a single target (which is usually the case). He can't even use two debuffs in a round without the Nue.

Hope – Synergist Crystarium

Character Hope
Role Synergist
Hope, like Sazh, eventually gets almost every basic Synergist Ability (though he gains Veil over Sazh's Vigilance). Until Chapter 10, however, Hope is primarily a defensive Synergist, with Abilities like Protect, Shell, and Bar-spells. Which of the two is more useful depends largely on how hard the enemy in question hits.

Lightning – Sentinel Crystarium

Character Lightning
Role Sentinel
Lightning is an interesting Sentinel, relying on the Elude Ability rather than Mediguard or Steelguard. This Ability (the only one she can use besides Provoke) allows her to dodge attacks with a very high rate of success. However, it only works on Physical attacks, making Lightning a sitting duck against Magic-wielding foes. Still, when it works, it's very effective and requires very little healing.

Sazh – Sentinel Crystarium

Character Sazh
Role Sentinel
Sazh is all about defense as a Sentinel. That may seem to go without saying, but he doesn't get any evasion Abilities, and while he does get Vendetta he does not get Entrench or the Counter auto Ability. He also doesn't get Mediguard, so if Sazh is your defender, you'll need to keep an eye on his HP. He does have the second-highest HP total in the game, though, and is the only non-primary Sentinel with Challenge.

Snow – Sentinel Crystarium

Character Snow
Role Sentinel
Snow is the prototypical Sentinel, gaining every Ability except Elude. Snow's job is to stand there and take punishment. While he has the same Ability list as Fang, Snow is a bit better as a Sentinel because of his high HP total and access to Weapons with the Improved Guard and Improved Ward abilities.

Vanille – Sentinel Crystarium

Character Vanille
Role Sentinel
Vanille as a Sentinel? Surely not! And truth be told, she's not very good at it. She has Mediguard at least, but not much else, including Challenge. She does have more HP than Lightning or Hope, but both of them are evasion Sentinels anyway. Basically, you don't want Vanille to be your main Sentinel. She's fine in the Tortoise (SEN/SEN/SEN) paradigm, but not much else.

Sentinel

Bonus Type Damage Reduction

Sentinel

Abbreviation SEN
Role Bonus Damage Reduction
Base Bonus (Self) Damage Resistance: +40%, Wound Resistance: +30%
Role Level I Bonus (Self) Damage Resistance: +45%, Wound Resistance: +33%
Role Level II Bonus (Self) Damage Resistance: +50%, Wound Resistance: +36%
Base Bonus (Allies) Damage Resistance: +7%, Wound Resistance: +5%
Role Level II Bonus (Allies) Damage Resistance: +9%, Wound Resistance: +7%
Role Accessory Defender's Topaz (Grants Damage Resistance: +3%, Wound Resistance: +3% to self)