The open-versus-closed argument gets treated like a team you join, complete with jerseys. It is not. It is a trade-off you make one job at a time, and the same person can sensibly land on opposite answers for two projects in the same week. What follows is a decision guide, not a leaderboard, because the leaderboard changes monthly and the trade-off underneath it does not.
What each side actually gives you
Open-weights models, the Llamas and DeepSeeks and Qwens of the world, hand you the actual model. You can download it, run it on your own hardware or a rented box, look at what it does, fine-tune it on your data, and keep the whole thing behind your own firewall. Nobody meters your calls. Nobody can change the model out from under you or deprecate it next quarter. If your data cannot legally or comfortably leave your walls, this is often the only real option.
Closed models, reached through an API, hand you a result. You send text, you get text back, and someone else owns the running of it. In exchange for giving up control you get the current frontier of quality, no infrastructure to babysit, and a model that quietly improves without you lifting a finger. For a lot of teams that is the entire pitch and it is a good one: you want the answer, not a second job running GPUs.
The costs hide in different places
People compare these on the wrong axis. They look at the per-token price of a closed API, see a number bigger than zero, and conclude that self-hosting an open model is cheaper. Sometimes. The closed price includes the hardware, the scaling, the uptime, and the salaries of people who keep it running. Open weights are free to download and very much not free to operate. You are now buying or renting GPUs, and someone on your team owns keeping the thing up at 3 a.m.
The honest version is about volume and steadiness. Spiky, low, or unpredictable traffic almost always favors the closed API, because you pay only for what you use and nothing when you are idle. Heavy, steady, round-the-clock traffic is where owning the hardware can win, because a machine you have already paid for does not care how many calls you push through it. The crossover is real, but it sits much further out than the sticker-price comparison suggests, and it moves every time GPU rental prices or token prices shift.
How to actually choose
Skip the identity and answer a few blunt questions about the specific job.
- Where is the data allowed to go? If it legally cannot leave your infrastructure, that decides it before any quality debate starts. Open weights, self-hosted, done.
- Do you need the absolute top of the quality range? For the hardest reasoning, the newest capabilities, the widest language coverage, the closed frontier models still tend to lead, and the gap is often worth paying for. For a well-scoped task, a mid-size open model may clear the bar with room to spare and cost far less to run.
- Does the model changing under you break things? If you have tuned prompts against exact behavior and cannot afford a silent update, a weights file you pin and control has an edge a hosted endpoint cannot match.
- Do you have people to run it? Serving a model in production is real, ongoing engineering. If that team does not exist, the API is not a compromise, it is the sane choice.
The gap keeps closing, the choice does not
The genuinely good news is that open weights have gotten shockingly close to the closed frontier on many everyday tasks. For summarizing, extraction, classification, ordinary chat, drafting, the practical difference is often small enough not to matter, and it keeps shrinking. That is a real shift and worth being cheerful about.
It does not, however, dissolve the trade-off. Control and privacy and the ops burden that comes with them sit on one side. Convenience and frontier quality and someone else's pager sit on the other. That tension is structural. It will still be here when today's model names are forgotten. The people who get the most out of AI are not the ones who picked a side and defended it. They are the ones who ask, for this specific job, which set of headaches they would rather have, and then pick accordingly.