Tower defense games are one of the most well-suited genres for playing on the go. Relative to other genres, they are fairly passive, and they allow the player to plant their towers, defend their bases, and only half focus. Of course, harder levels require a more active approach, but it still lends itself well to playing on iOS.

A vast variety of tower defense games exists on the App Store. Gamers looking for choice in the genre have plenty of options, but for those who just want to a few premium games, deciding can be very difficult. Don't worry, we are here to help!

Today, we're putting two of the more popular tower defense games on the App Store head-to-head. In an interesting clash, we have Fieldrunners 2, which comes with a $2.99 price tag, and Towers N' Trolls, which is a free-to-play game supported by in-app purchases and ads. Both are featured on our Best iPhone Games page, so they are both top quality.

Is Fieldrunners 2 worth the cost? Are the in-app purchases intrusive to the experience in Towers N' Trolls? Most importantly, which game is more fun? Keep reading to find out.

Tower N' Trolls (Free)

In Towers N' Trolls the tower defense gameplay is pretty standard. Waves of enemies walk toward the end of the level, and for each one that gets through, you lose a life. To stop them from getting to the end, you are planting a variety of towers. The game differentiates itself with the use of special abilities such as land mines and exploding powder kegs.

There is plenty of play time to be had out of Towers N' Trolls. In all, there are 65 levels spanning 10 different worlds. These are unlocked using gems, which can be purchased in-game or earned through playing the tower defense game. There is also the option to unlock all the worlds for $7.99.

From a visual standpoint, the game looks good. The animation is smooth and solid, and the HD version of the game looks nice on a Retina display.

Overall, this is a solid tower defense game. Will it blow you away with some incredible twist to the formula? Definitely not, but that doesn't mean it's not worthwhile, especially considering it is free. Yes, there are in-app purchases and the occasional advert but thankfully they are not too intrusive and  don't ruin the game at all.

Fieldrunners 2 ($2.99)

While Fieldrunners 2 might costs three bucks, it is widely regarded as one of the best tower defense games on the App Store. We've already established that Towers N' Trolls is a great tower defense game, and it's playable for free, so is this premium title worth the cost?

Fieldrunners 2 breaks the tower defense mold by having the player draw the path for the enemies with the placement of the towers in some levels. Now, this is good if you want a change, but if you are looking for a pure, traditional tower defense game with pre-drawn paths, this might throw you off a bit. Of course, there are plenty of traditional levels, so fans of the old-school games will get a taste of that as well.

The gameplay in Fieldrunners 2 is extensive, so there is a lot of value to be had for a small $2.99 purchase. All the levels are available without needing to spend any extra money, but there are still in-app purchases if you want additional coins to help you earn more power-ups. Personally, I am not a fan of in-app purchases in paid games, but in Fieldrunners 2, it is completely optional, so I will give it a pass.

Visually, this is a beautiful tower defense game. Every detail from the towers to the map looks amazing. It's clear that a great deal of time was put into the art, and it makes staring at the levels as waves and waves of enemies attack a much more enjoyable experience.

And The Winner Is...?

When it's all said and done, I have to go with Fieldrunners 2 here. Yes, it costs $2.99, but if you were to purchase the level pack in Towers N' Trolls, it would cost more than double that amount. Of course, I am not taking anything away from Towers N' Trolls, as it is fine example of a tower defense game, especially when you consider that it can be played without spending a dime.

Still, if you only have the time to play one of the games, I am comfortable recommending Fieldrunners 2, even if you wait for it to go on sale.

Have you played these two tower defense titles? Which is your favourite? Let us know what you think by leaving a comment below.