Modern Combat will give you the bang for your buck
There are 6 modes to play: Deathmatch, Team Deathmatch, Domination, Boom and Bust, Escorting and Extraction, some of which are map specific. You also get 5 different but overall decent maps to play in. As you gain experience you will level up and unlock additional attachments or weapons such as sniper rifles. But that doesn't mean you can simply chose to play with assault rifles or sniper rifles like in Call of Duty, here you have to earn enough money to actually buy them in each match, since money gets reset between matches.
You start off with a pistol, for which there is no need to purchase, and have an option of purchasing frag, smoke or stun grenades, armor and helmet for additional protection, or between 2 sub machine guns and 2 shotguns. If you take the armor, you wont have enough money to take anything else and will be forced to play with a handgun, but you can take a good weapon instead and play the round without armor. You also have a knife that works similar to Modern Warfare, but the hit detection is poor, so you cannot really rely on it too much, instead will prove only useful to take down unsuspecting campers without giving yourself away. Once you die, you can take control of a friendly bot, and this is really a good feature from those game modes where respawning is forbidden until the end of the round.
All of the modes can be played with AI bots, who can sometimes be brutal but sometimes really stupid. Bots will try to play like real human players would, so they wont notice your presence if you approach from behind, instead will only start attacking you if you start shooting first, or come into body contact, or if you're obviously in their line of sight, but sometimes bots will even stand right in front of you, staring for appears to be minutes without realizing you're their enemy. Sometimes their accuracy is really bad, and other times they can headshot you with a shotgun from miles away. When you die you get to see who killed you and where they were, but you don't get to see where he is heading next.
Another real cool feature in Modern Combat is the Move support. It works really well and is a lot of fun to play with. One of the buttons on the motion controller is used to lock your view, so you stop turning around and can aim anywhere on the screen, I find this very useful and something that every shooter with Move support should have.
Searching for matches is also very good, you can pick to just play a random quick online match and leave everything up to the game to connect you somewhere, or you can specify exactly which map and which mode with all other parameters it is that you would like to play, if no matches of your choice currently exist, you can simply create it, play with bots until people start joining. There appears to be a lot of people playing online.
Modern Combat has a lot of good stuff going on for only 9$, but there are also some things it performs poorly. The loading times can seem extremely long, especially those that take place after each round and you have to play 13 rounds in each match. But its not a big issue for modes like Domination or Deathmatch where you get to play up to 30 minutes without seeing a loading screen and take a minute to rest. Occasional respawns can lead to fast unexplained suicide, even though nothing exploded, and the killcam is focused on yourself as your killer, but this also happens very rarely. The experience is accumulated at a frustratingly slow pace, so even after 20 hours of playing, you will still be level 15, without any decent unlockable attachments, so by the time you feel any progress, you will have played all combinations of maps and game modes at least a thousand times and will probably get fed up with everything. One more thing that seems to be annoying is the death delay, most of the time, enemies will die a second after you have actually shot them, and this can lead to some troublesome situations like wasting ammo on something that is already dead but still appears to be standing, and also increasing the attention required for every target that you shoot at.
With all its shortcomings, it is definitely worth the 9$, if you like competitive and fairly balanced shooters with great Move support you wont regret the money spent.