38 Special really isn't a terribly strong round. If over penetration is a major concern for you, then you're already working with one of the safer cartridges with respect to that. Corbon makes some great products, but you really have a lot of good options out there for your caliber with a good number of different brands. The Federal Hydra Shok has been a very popular defensive round for a long time now.
Now to the old myth that birdshot is safer and/or won't penetrate walls... That's just not completely true. Think about the distances you'd be shooting in a home defense situation. Often no more than 10-12 feet, depending on the layout of your home and size of the rooms. At distances like that, birdshot can still be incredibly destructive because the shot has barely any room to spread before impact. Consider that a standard 2-3/4" shell of any small hunting shot still contains 1 ounce of metal projectile. Also keep in mind that most defensive type shotguns have a cylinder bore. The spread of your shot will vary depending on the exact ammo type, but the general rule of thumb with a cylinder bore is that the shot will spread one inch for every yard it travels from the gun. A choked barrel can hold an even tighter pattern, intensifying the effect I'm describing here. So if you're shooting 12 feet across a room with a cylinder bore, the spread pattern of your 1 ounce of shot is likely no more than about 4 inches in diameter. If you hit your target with that, he's going to have a very bad day. However, if you miss with your birdshot from such a short distance, it will easily travel through a typical interior wall and inflict heavy (easily lethal) damage on whatever it hits. Just something to consider.
Here's a video that illustrates my point. It's not great quality, but you can get the idea.
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