Higher AL offset extra protection?

I'm down in Maguuma area and have a complete set of Ventari Bonelace armor - that's 225 total AL and +15 against piercing on each of the 4 body pieces.

I got a face scar and gloves from collectors that are AL51 and am wondering about the other pieces. If I get the other 3 pieces, that will be a total AL of 255, but no extra protection against piercing damage.

Would that give me more overall protection, making up for the loss of the piercing protection?

I could just add the boots and keep the Bonelace tunic and leggings.

Which would be the better option?

Not really, if a Piercing attack hits you, its going to penetrate your set armor level. With the extra protection, you're gonna be more protected agaisnt piercing attacks.

The problem lies in the difference in armor. You get more protection from all types of damage, but lose protection against penetration damage.

damage is location specific. You don't "add up" the AL. Test it.
If you wear no armor except chest piece, you will see that soemtimes you take a lot of damage, sometimes very little.

i.e. hit to chest doesn't count other pieces' effects (runes count, the ACTUAL ARMOR doesn't). (the only exception to the rule is the knight armor's absorbtion stat that is blanket reduction)

total AR doenst mean a thing as the armor rating is per piece not added up like other games

Taken from http://www.gwonline.net/page.php?p=157#Armor

Armor in Guild Wars works in an interesting, yet effective way. There are 5 body locations in the game - they are your head, arms, legs, feet, and chest. When a player is hit for damage, the game randomly determines which body location gets hit. Player positioning (e.g.: hitting from the side or from above) as well as what skill is used (hamstring or skull crack for example) can force a character to hit a specific body location of the target, or at least increases the chances of you hitting that location. The chest has the highest chance to be hit, followed by your legs.

Once a hit location is determined, the game uses the Armor Level (AL) from the armor on the hit location for the damage calculations. When it comes to spells, the hit location is nearly always the chest, unless the spell causes a projectile to fire at the target (e.g. lightning orb) in which case the hit location is randomly determined as usual

Data researched and compiled by SonOfRah.

Don't forget the +15 AL while Casting that Mesmer's Courtly armor has. That +15 AL is also a global effect - thus only need 1 piece of it to get the full bonus all over, same as with Knights/Ascalon damage reduction.

Yes, I realize that the +15 against piercing is per location, i.e. *not* +60 total against piercing. But I was forgeting that all armor is 'per location'.

So, while the AL51 pieces would offer a bit more protection against hammer, axes & swords, they would actually be less effective against bows than the AL45 +15 piercing Bonelace pieces, right?

On the same point, are all projectile attacks, like devourers and spiders, considered piercing?

Technically not all projectiles are piercing; however, all projectiles similar to the ones you listed are. Projectiles that wouldn't be considered piercing include wand/staff attacks and things such as the Frost Giants later on who throw boulders and do blunt damage.