Model 10 Smith 4 inch. Keyboard commandos will depricate the .38 Special and some advocate a shotgun but:
A .38 will make an assailant fall down if properly applied and is very manageable for recoil and retention.
A shotgun will not spray a whole room as in the movies; it will spread to about 10 inches in 20 feet. In the confines of a house, a strong, determined attacker can overpower you and take an unwieldy shotgun away from you.
Unless you shoot him first. When investigating something use a handgun. When it comes down to fighting, it would be foolish to use a handgun in most situations when the power and shootability of a long gun are available. If one were to only have one gun, then yes, it should be a handgun.
As far as the .38 spl. goes, I wouldn't tell someone not to get a gun such as a model 10 if that were available, used, at a reasonable price. At the same time why seek one out when the same ammo will work in a .357 and more powerful ammo can be used if desired?
Regarding Taurus and Charter Arms and Rossi, you have been given good advice, avoid them. If you're looking to save money, shop used and get a S&W, Ruger, or similar quality product.
When it comes to the 870 Express, I've heard a lot of people complain about quality issues, including a finish that, on many guns, rusts if you look at it wrong. Personally I think Express guns are good servicable pieces, but if I were in the market for such a gun, I would look for a used Wingmaster, or Police model instead. They are better built.