I own a Mossberg 590 Shockwave, and while it's obviously true that it isn't as easy to shoot accurately as a Shotgun with a conventional stock, it's a far cry from inaccurate or otherwise impossible to hit anything with.
The Shockwave's Raptor Grip is a completely different animal than your typical Vertical Pistol Grip, as it doesn't transfer the recoil straight back into the wrist, but rather off into space. Many folks (myself included) are shocked (pun not intended) to discover that the 590 Shockwave has very little felt recoil compared to other Shotguns, simply because it just isn't transferred into the shoulder or wrist, so all you feel is a little jolt when you pull the trigger.
Furthermore, because the recoil isn't that fierce, contrary to popular belief, you can hold it up, aim down the sights, and fire the gun without it whacking you in the face. By utilizing a simple push/pull method to brace the gun, it is possible to pull off fast, accurate, safe shots with the 590 Shockwave, which can be verified by watching any experienced shooter on YouTube firing one.
Heck, even if you're not confident/comfortable shooting the 590 Shockwave while holding it up to eye level, it can still be fired fast, accurate, and safely by simply tucking the end of the grip between your bicep and pectoral muscles.
So while many folks are bound to come in here ignorantly proclaiming how a gun they've never fired or otherwise put absolutely no thought/effort into firing is impossible to score accurate hits with, not to mention how Grizzly Bears absolutely cannot be dropped by anything short of a 20mm Vulcan, take it from someone who actually owns a Mossberg 590 Shockwave; you absolutely can shoot one fast, accurately, and safely.
What's more, I think that a 590 Shockwave loaded with Brenneke Black Magic Magnum Slugs is just about the best weapon for Wilderness Defense that anyone could buy without spending a lot of money.
The Mossberg is small, lightweight, quick to deploy, and far easier to master than anyone would expect. Yes, it's larger than say a Smith & Wesson Model 500 Magnum Revolver, but it's also easier to control with two points of contact, more powerful with Brenneke Slugs, and only just a little bit heavier to boot. Plus, being a Pump Action Scsttergun, just about the only way that it can malfunction is if you shortstroke the slide, but seeing as you really only have time for one well aimmed shot at a charging bear, and you aren't realistically going to need a second shot with a 3" 12 Gauge Magnum Slug if you do your part, the only thing that you have to worry about is your own ability to take the shot.
So, I say; go long with the 590 Shockwave... *throws football* I do.