Regarding buckshot, I see that Federal's reduced recoil 00 has nine pellets and a listed muzzle velocity of 1145 fps, while Federal's regular 00 has nine pellets at 1325 fps. So obviously, you've got the same number and size of projectiles, but they're just moving a little slower. Still, the 00 pellets provide enough momentum for adequate penetration. I think some reduced recoil 00 loads (from other brands) have 8 pellets instead of the usual 9. I don't think this would be a deal-breaker either.
I've never heard anyone who is an expert on the subject say anything bad about reduced recoil defense loads. You'll hear some people say 3" shells are the surest bet, but I don't believe many of those people are defense instructors or anything like that.
I'd be a little more reluctant to use reduced recoil buckshot for hunting, just because we're talking about greater distances over which the pellets will lose more of their penetrating capability.
Regarding slugs for hunting, killing power generally hasn't been the limiting factor. More likely, a hunter's range is limited by a slug's accuracy and rainbow trajectory. In fact, 20-gauge slug guns are growing in popularity because people are realizing that--at the relatively short distances at which shotguns can provide good shot placement--super powered slugs aren't needed for most deer. (this may be a different story if you're thinking of hunting big hogs or bears)
Remington's "Slugger" (their basic rifled slug) weighs 1 oz. and has a listed muzzle velocity of 1560 fps. Their managed-recoil Slugger is also 1 oz. but starts at 1397 fps.
Unlike some high-velocity rifle cartridges, slugs aren't relying on hydro-static shock or tremendous temporary cavitation to kill game. Slugs generally kill by creating broad, deep permanent wound channels. For this type of damage, velocity isn't especially critical.
Reduced recoil slugs will still likely kill deer out as far as your accuracy and trajectory allows.
