So what are the difference between them? I bought some 75 grain taps for home defence and now I see there are 55 grain as well. Help.... the only thing I can see is that the 55 grain stuff is faster.
One's 75 Grain bullet, the other is a 55 grain bullet...
Yeah, I know.
When you buy TAP ammo, it's likely you're buying for self-defense or home-defense. You want to buy the most effective bullet for your purpose. If home-defense, I'd go with the 75 grain regardless, such a short range, accuracy won't be an issue.
If you are using them for longer range (50 yard and up), then you should get the heaviest bullet that works well in your rifle. the 75 grain will work best in a 1 in 8 or 1 in 7 twist rifle. If you have a 1 in 9 twist, look for a 68 grain bullet, but 55 will work as well.
And take them out to the range and test them. Some 1 in 9's will fire 75's just fine, I have a stag 1 in 9 rifle that runs them great with no keyholing. Others complain about accuracy in that config.
At home defense ranges, I don't think accuracy or key holing will be much of an issue, though.
55gr TAP is a varmint bullet and ill-suited for defensive use, regardless of how Hornady markets it.