I wouldn’t say one is better than the other, but I think one can be more helpful. A rejection that is personalized with feedback will give you something to consider as you continue to revise and tune your project. Of course, take that feedback with a grain of salt, because it might be personal to the agent. This means that what the agent said might not be an inherent flaw in the manuscript, but just something they personally didn’t like. Agenting is extremely subjective, so that is something to always consider when looking at feedback in a rejection.
That being said, a form rejection isn’t a knock on your writing. Remember that agents are (in general) not paid for reading and responding to queries. We’re doing this on our own time in hopes that we find projects we can sell and earn money in the future. Some of us can’t spend the time to give personal feedback on every single query we receive. It would take up hours of our time that we can’t afford to give up without pay. I know form rejections can be discouraging, but sometimes they are necessary from our side. We don’t like using form rejections, but we have to in order to keep focus on our clients and working to build ourselves as agents.
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