So lets take a look at what each one does, and see which ships, and which other upgrades, works best with each one.
This article is part of the Upgrades series.
Enhanced Armaments - 10 pts - MODIFICATION - An expensive upgrade, Enhanced Armaments increases the battery armament for both side hull zones by 1 Red dice. This upgrade has two potential uses - making a ship with less ideal side armament have a better shot out it's broadside, and increasing a ship that already has a devastating broadside that much scarier. Note that it is a Modification - you are limited to one upgrade with Modification per ship.
For the Victory, it increases your long range dice on all arcs except your rear to the same 3 Red, a bit pricey for that solution, but it gives you and your poor turning ship a little extra juice for dealing with flanking enemies - probably about the time that you really want that enemy dead.
For the Rebels, it has the most synergy with the Assault Frigate, particularly the AFIIB. Taking the ship's biggest asset - a huge, high damage side arc - and making it better by adding another dice. Being able to shoot 4 long range dice means that the AFII outguns everything else in Wave 1 at long distance, as long as it can keep that range. The other ships have less benefit from the upgrade - the CR90A becomes a ship with the same guns on the front and sides, but it already has excellent maneuverability and Command Value of 1, not really needing the extra flexibility. Also, the upgrade adds nearly 1/4 of the initial point cost to the ship in the form of a single upgrade - maybe not the best decision. The Nebulon B is a slightly different story - with Enhanced Armaments, and a very small front arc, it can use the upgrade to double-arc enemy ships as they get closer, increasing the damage it does to the enemy when they have just started to clear its front arc. Maybe not the best option to throw 10 pts on a ship where you'd only use the upgrade to do extra damage when you are out of good position, but a thought worth considering.
H9 Turbolasers - 8 pts - H9 turbolasers let you change 1 dice that you rolled a Hit result or Crit result with to an Accuracy Result. An excellent upgrade for dealing with enemies that have very annoying defense tokens, such as a single brace. It is a better gun the more dice you are throwing, but trails off in usefulness as your Blue dice increase, as you're more likely to roll multiple natural accuracies.
For Imperials, it works the best for a Victory I-Class to guarantee accuracies when you get someone at close range with your big front arc, or for the Warlord - not only can you guarantee one double Red hit so long as you roll a hit or crit, or an accuracy result, but you can also guarantee every anti-fighter shot it takes is a hit.
The Rebellion can use this to a certain effect on the Assault Frigate, particularly the AFII-A variant that wants to double arc the enemy instead of Gunnery Team broadside them anyway. Plus you are guaranteed a hit result to use this with by having 1 Blue in your dice pool. For the Nebulon B, it can be used to ensure that a long range front arc attack dice hits for decent damage (say a double Hit or Salvation Crit result), and aren't absorbed by evades, or that a huge, high variance roll isn't wasted on a brace. The CR90A, which is shown on the card art, is perhaps ironically the worst ship to equip this upgrade, only being able to roll a limited amount of dice in the first place.
XI7 Turbolasers - 6 pts - Note that it is X"i"7 and not X-Seventeen. XI7 lets you weaken the enemies redirect tokens, forcing them to only redirect 1 point of damage onto another hull zone.
For the Victory Class, this card is more of a threat, than an upgrade. Very good against mirror matches of Victory vs Victory, it limits the biggest defensive benefit the Victory has (double redirects) and turns it into a single point of damage mitigated before punching into the hull.
For Rebels, the XI7 comes with and works best with, the Nebulon B Frigate, particularly the Salvation. Turning the Salvation's already dangerous Red dice into a lance of hull damage.
EDIT: As of 10/16/15 and the release of the new FAQ, Advanced Projectors no longer are a soft counter to XI7s, and in fact the XI7 is a had counter to Advanced Projectors. This changes the major use for XI7, putting it as an excellent upgrade to take against enemy ships that have low hull and rely on their shields for defense - the same ships that would be taking Advanced Projectors.
XX-9 Turbolasers - 5 pts - Crit Effect - The first 2 damage cards dealt to the defender by this attack are dealt face up. Replacing the standard crit effect to 2 damage cards face up makes this an upgrade that works best with high damage ships. So, pretty much worthless on a CR90A. It also doesn't work with other crit effect cards, so those are right out. It also has a huge synergy with Precision Strike - flipping up 2 cards for a potential 3 (2 from the crit effect and 1 from a hit spent) victory tokens per attack on a weakened enemy.
There is something to be said for putting it on a Victory I-Class along with Expanded Launchers - a good chance of dealing significant damage to an enemy at point blank range, and flipping two cards up. It also goes well on any Victory Class - with a natural 6 dice front arc, you're almost guaranteed a crit result, and the most likely to punch multiple damage through onto a ship's hull.
This also goes well with the Salvation or Paragon - rolling lots of dice and doing considerable damage means you're more likely to get multiple hits on the hull. Again, upgrading the CR90A with this is less useful.
That is it for Turbolasers. Next time we will go over Ion Cannons! Until then, fly casual.