Best answer I got to this question is whatever physical thing you enjoy, that you can do regularly. I'm sure you can debate swimming vs running vs deadlifts, and come away with some useful answers, but the biggest problem is finding something you can make yourself do as often as possible. I started walking a lot more, two long walks a day, as I enjoy it. I still run sometimes, but that's hard work, and harder to keep up a schedule if I kind of dread it. Consistency and scheduling help you reliably be active.

However, for just losing weight, eating fewer calories is better than exercise. 30 minutes hard running is, based on a lot of factors, probably between 200-500 calories burnt. If all you want to do is lose weight, you're probably better trying to eat that many fewer calories instead.

In the real world, both is good. Also, I find that exercising some helps keep me feeling less tired (which happens when I eat less). Downside is working out makes me a lot hungrier, which makes the calorie deficit harder to hit.

Also, for health, you should still do some hard exercise that get your heart rate and breathing rate going for a few minutes at least a few times a week, but tbh if it's just a workout for 5 min, it probably isn't burning much calories. But that fives minutes of high BPM help keeps your cardiovascular system in shape.