Hi there,
I have owned a Benelli Nova H2O Tactical (the all-weather nickel-plated variant) and a Benelli Supernova Tactical (SNT) for several years. I previously owned a third SNT with rifle sights, but sold it when I picked one up my current example with the factory ghost ring sights fitted. Both of my SNTs have been factory pistol-grip examples; conversely, like all standard Novas, the H2O is not available in pistol grip configuration.
Bottom Line Up Front: The only other pump shotgun I would consider owning outside of a Benelli SUPER (important distinction from standard... more to follow) Nova would be a Winchester Model 12... which I have also owned. I have fired thousands upon thousands of rounds from all of my Nova variants over the years, and have not had one malfunction. 2 3/4 to 3 1/2 shells with not one stovepipe or jam. Nothing. These are the only weapons I have ever owned where I can make this statement.
For reference sake, here are a couple of my observations between the Nova and Supernova (SN): The Nova is a cheaper gun than the SN or SNT. The majority of the moving parts are the same and interchangeable, but the Supernova is a modular design and has interchangeable stocks, a larger triggerguard, and thicker polymer on the receiver. Also (critically) the SN has a factory drilled and tapped receiver. The SN feels more robust than the regular Nova, but the function of the guns is identical. A SN is typically ~$100 more than the standard Nova. SNs are not available in 20 gauge, or in youth configuration; regular Novas are.
I would compare a standard Benelli Nova favorably to a modern Remington 870Police. Conversely, and although it is a matter of opinion (wood vs polymer, etc), as a tool, I believe the Supernova is superior to even old-build Remington 870Ps in virtually every way. Both Benelli's are in a different league than any of the modern Cerberus holdings Remington express variants, or modern Mossberg 500s.
Although it is "cheaper" than the SN, the standard Nova is an extremely robust gun. From the factory, all variants come equipped with magazine plugs/limiters (that are easily removed). There are factory extensions available without too much hassle for ~$120. Aftermarket extensions are readily available for ~$100. I would stick with factory for everything, but that's just me.
All Novas and SNs have a magazine stop button on the foreend that allows you to rack the slide without chambering a new round. This enables you to remove an unfired cartridge from the chamber WITHOUT releasing a round from the magazine. Furthermore, all variants have a cartridge stop lever that automatically catches when you begin chambering rounds (i.e. you don't have to hold the carrier down with your thumb when inserting rounds into the magazine).
With this in mind, the only reason I own a regular nova is because I wanted an H2O variant as a hiking/camping gun, and the factory does not currently make a nickel-plated SNT. The SN/SNT is a higher quality weapon that is, as far as I'm concerned, the gold-standard of modern pumps. If Benelli ever releases a SNT in H2O configuration, my Nova H2O will be out the door.
Common complaints regarding Novas and SNs are the lack of accessories. I have a TacStar sidesaddle on my H2O that was easy to procure. For SNs and SNTs, Mesa Tactical makes an outstanding combination sidesaddle/upper rail that utilizes the factory mounts. All of my Nova's have been equipped with factory extensions that I located online without issue. Factory collapsible stocks are available for SNTs, but they are expensive. Insight Technology makes a superb adapter that clamps to the magazine extension on my Nova and SNT. Both of them are equipped with Insight M3X lights. I'm not really sure what else you need accessory-wise for a shotgun, but this has been about it for me.
True, if you want some kind of crazy light-equipped "tactical" foreend (that lacks the shell-stop feature of the Benelli forend in the first place...), or a neon green "Zombie Slayer" engraving on the side... then you'd better look to Wal-Mart for an 870 Express or Mossberg 500. I'm 100% fine with "accessories" like this not being available for a Benelli. YMMV.
Final thoughts: If at all possible, get a SNT or SN vice a standard Nova Tactical or Nova. I liked the factory SNT ghost ring sights better than the rifle sights, but this is a matter of choice. As is standard with all firearms, I would shoot them first to make sure they fit you. Hope this helps.
Take care.