The key is being honest with yourself about what you'll actually use. If your only need is to check your heart rate without looking at your phone, a budget or mid-range sports watch like Amazfit will do the job and save you a lot of money. But there's a detail that others don't mention: Apple and Samsung smartwatches hook you with other features you'll discover along the way, so before you decide I'd recommend thinking about whether you'd really never use notifications, maps, music control, or more advanced workout tracking. It's easy to fall into the trap of thinking "I only want the heart rate monitor" when in reality having everything on your wrist ends up being useful.
That said, the ecosystem matters a ton. If you already have an iPhone or a good relationship with Android, high-end watches win on integration and ease of use, but you pay for it. My recommendation would be to set a maximum budget (say, half the price of an Apple Watch) and search in that range: there are options like Garmin, Amazfit, or even Chinese brands that'll surprise you. Besides, a smartwatch isn't really essential in 2026; most people still get by just fine checking their phone now and then at the gym.