This is a common idea, that a bolt or lever action firearm is even remotely comparable to a semi-auto when it comes to self defense or use in combat. It's false, completely false. In practice, such guns will give you a single shot, which if you miss (and you almost certainly will), you lose the opportunity. Either you get shot yourself, or your adversary ducks behind something. A semi-auto will give you several shots. Typically it is the second or third shot that actually hits. The idea of being a super accurate "sniper" is videogame bs. You are not any more or less likely to hit your first shot with a bolt-action than you are with a self-loader. You are however less likely to hit follow-up shots, if you even get the chance for them because it takes so long to require. Every military in the world has spent a ton of time and effort studying this and they all agree on these facts. Most of the combat effectiveness of a bolt-action rifle comes from deterrence and morale effects, rarely do they actually hit anything when you are also playing with machine guns and artillery.

That being said, a gun you know how to use will always be better than one you don't. And for the exact same reasons, the gun you have is always better than the gun you don't have. But don't make the mistake of crippling yourself and putting yourself at a massive disadvantage by using a manually loaded gun when you can help it.