Whoo boy, you couldn't have picked more opposite ways to go forced induction.
It's gonna depend completely on what you want. 90% street, 10% race duty is totally irrevelent.
The KenneBell supercharger is a twin screw positive displacement unit. It runs off a drive belt, and delivers maximum boost at a mere 1800rpms. With some mild engine mods you should expect to see 100hp additional with the 8psi kit. Stock, you'll get around 80hp. The KenneBell is a stealth unit, making no real audible whine. It's a bolt on part, requiring no oiling lines or fabrication. The installation is as simple as it gets for this type of system. Gearing won't need to be very aggressive to get good times at the strip or on the street. The KenneBell turns your smallblock into a bigblock with teeth. As with any forced induction unit, adding cooling upgrades is a good idea. Simple to bolt in, extremely low maintenence and flexibilty in making power is what the kit does best.
The Incon turbo kit is a dual turbocharger set running off exhaust pressure to spin impellers making tons of boost. You'll have to get some rpm before the kit starts making maximum boost, when it does you can expect much more hp than the KenneBell will give you. This system is noisy, you'll definately hear the turbo's spooling, so will the guy getting blown away next to you. With some mild engine work 150hp+ additional is completely attainable. The kit is much more of a pain to install, and the initial cost is higher. You should upgrade your cooling system, just like with the KenneBell. Gearing should be a little more aggressive than with the KenneBell for best results. This way is expensive, but with it you get huge power, and even greater cool guy factor.
It's up to you, myself personally, I like the KenneBell for reliability. I don't think I'd like putting that much more hp onto a stock block/rotating assembly. That and I want to be silent but deadly.