If you’re a shooter fan and you have either an Xbox 360 or a PlayStation 3, then the month is a good one for you.

If you’ve got both systems, you likely have a choice to make.

The sequels to each system’s blockbuster shooter each came out the same week: “Gears of War 2” on Xbox 360 and “Resistance 2” for PlayStation 3.

On the surface, the two games are a lot alike. Both involve fending off aliens, although “Gears” takes place on another planet. Both have a male protagonist, lots of big guns and fun multiplayer.

But they’re not the same game, and each has its advantage over the other.

Let’s start with “Gears 2.” Once again, you play as Marcus Fenix, a gruff sergeant of Delta Company. The last game ended with Marcus and his squadmates — including Dom, who also returns — setting off a gigantic bomb in the underground lair of the Locust Horde.

Unfortunately, the bomb only made them more angry. Now, the guys of Delta, plus some newcomers, find themselves again hunting down the Locust leader and trying to prevent the Horde from sinking all of their cities.

“Gears 2” is a third-person shooter, though if you’re like me, you’ll nearly always be zoomed into the over-the-shoulder aiming mode.

The cover system is one of the “Gears” series’ highlights. Tapping the A button makes Marcus roll or dive behind walls and columns. He then leans out to shoot, minimizing damage. It worked well in the first game, and it works well now.

Favorite weapons return, including the main Lancer Assault Rifle. This gun has a chain saw on its front, and “Gears 2” adds in the ability for very cool “chain saw duels” between two combatants with the Lancer equipped.

Fun new weapons include mortars, a flamethrower and a poison-releasing grenade.

Other new gameplay elements include the ability to attach grenades to walls and stylish, ultra-violent new execution finishing moves.

One of the best things about the first game was its co-op mode, where one player played as Marcus and one as Dom. This returns, and it’s better than ever because of independent difficulty levels. Someone who’s really good can play on hardcore while his partner plays on casual. The difference is made up in how much damage each character can take.

The single-player campaign is fun, but so is the multiplayer, and that has been tweaked as well. A training ground for practicing has been added, as has the ability to use bots. Parties online now can have five members instead of four, and new game modes have been added.

Perhaps the best new addition is Horde mode, in which a team of up to five players fights off waves of increasingly difficult enemies.

“Gears 2” doesn’t make any drastic changes, but all of its new features enhance what was already a fantastically fun experience. Despite some overly cheesy and cliched dialogue, the story is interesting and a blast to work through, especially with friends.

Resistance is futile

“Resistance 2” similarly makes more enhancements than true changes.

“Resistance” is a first-person shooter. The aliens, called Chimera, are trying to take over Earth, and they can infect and convert humans. The lead character, Nathan Hale, is one such infected, although he keeps it in check with drugs.

The first “Resistance” took place in an alternate-history 1950s England. The second is 1950s America. Battlegrounds vary from San Francisco to Utah to Chicago.

Easily the coolest new thing is the game’s scale. Bosses are massive, and defeating them often means multiple attempts spread throughout the story. It gives the game a more epic feel.

One of the things I like best about the “Resistance” series is the weapon selection. Each weapon has a secondary function that’s useful in its own way. Some, for example, create a protective force field, while others toss out grenades. I love the secondary functions.

The single-player campaign is fun, if a bit dull storywise, but online multiplayer is where “Resistance” shines. A massive 60 players can compete against each other online in different game modes. Even with the large number of participants, I noticed no lag while playing, which is quite an accomplishment.

In addition to the competitive online, “Resistance” has a cooperative mode, both online and off, in which players choose a class to play as and work together to meet objectives.

Experience is earned across all three forms of gameplay, and achieving new levels unlocks character skins, accessories and other perks.

“Resistance” keeps track of an impressive number of statistics, both in-game and at MyResistance.net, and it’s easy to check your friends’. Ribbons and medals also are awarded for meeting certain criteria.

Developer Insomniac brags that achieving everything in the single-player, co-op and competitive gameplay adds up to 420 hours of playtime. That’s pretty crazy, and awesome if you’re into shooters.

“Gears 2” and “Resistance 2” are both an evolution of stellar first games. Both are fast-paced and well-done and will entertain for quite some time.

My suggestion is to buy both. Seriously. You won’t regret it.

However, if you’re truly limited to just one, I’d say go with “Gears” for its single-player campaign and “Resistance” for online.