I have no first hand experience with Intova cameras. I've read reviews of many that say they are moderate cameras but not great.
I bought the sealife 100% because of the "piano buttons" on the housing. I've had a couple of underwater cameras with smaller buttons and they were very hard to use, even snorkeling without gloves. The piano buttons are smooth operating and large enough to hit one button at a time with heavy gloves on, as opposed to hitting several buttons at a time.
I haven't been too impressed with the above ground pictures I've taken so far with my DC1200 but it was low light conditions so perhaps I just didn't fiddle with it enough. I'll be testing it in the water for the first time tomorrow. The sealife also has some features you can't access through the housing, like changing some of the picture settings etc. As a "point and shooter" type person, when in the water, I haven't needed a lot of settings changes while swimming. It switches from video mode to picture mode with the housing but you need to set which picture and video settings you want before putting it in the housing.
If price is a big factor, go with the Intova. For the extra $200 of the sealife you can buy an external strobe and have a "full" kit.
If easy to use buttons are your goal, the sealife is very difficult to beat.
I'll respectfully disagree with G1138 as far as the strobe arms for the sealife. The ones I've played with so far (didn't buy one yet) were fully capable of contorting into any position and quite flexible. I don't know about length versus other options, but they don't seem significantly shorter than the couple I've seen (but not handled) that are equivalent price point.
I would agree with PatW that the ability to shoot RAW is a great bonus but I haven't found any cameras in that price range that have the ability. I could have missed some though.