I think that I giant is much better then a hellcannon for the points you are paying.

Pro's of Giant,

Stubborn 10 has crazy attacks that can ruin an army, like yell and bawl, jump up and down, pick up and eat, all kinds of crazy stuff. Causes terror, etc etc.

Con's: Only T 5 and can be taken out easy by missle fire and magic.

But I think that in the right hands Giants can be the winning unit in a battle over and over again without any major problems.

Pro's of Hellcannon,

Unbreakable, T 6 S 6 five attacks and can shoot. Good for taking out large blocks of guys.

Cons: Which I think out weight its reliablity

Needs to take leadership every turn to do anything. If it misfires crazy things can happen, both good and bad.

Well I could keep going but what do you guys think.

Also me scooter lincoln and Kaleb rolled out a one on one fight giant vs hellcannon,

Giant one 3 to 1 and tied one for me and lincoln and for kaleb and scooter giant one 4 to 1

I've had both units do nothing, and both units do really amazing things.

Against stuff like rat ogres and other units of big things, the giants attacks are not nearly so good as they are against a single monster, especially if it has MoS. I've been using one of each for most games. If I had to choose, I'd go with the hellcannon

Never had too much problems dealing with Giants. They are a primary target but usually go down on turn one or two.
Bolt Thrower, Doombolt & Manbane assassins all work well against them.

Hellcannons have a better surprise value since people take them for war machines, but being able to charge a flanker and tarpit them for a turn or two is almost as good as whatever you get out of their shooting

I have never had a Giant die in a battle until the last time I played Lincoln, but other then that had about 20 battles where I have always managed to keep them alive, because I hide them and use them very smart, it just depends on your tactics. But if your playing against chaos which I have many times and they have a hellcannon they are going down cause I'm taking my giant right at them.

And chaos giants are even better because you can make them always strick first!!!