These are rabbits. They live very harsh life. They don't live long. They can, they are biologically capable of living many years, but they are prey for nearly everything. They also breed like rabbits. If they didn't all get mostly eaten every year we would be knee-deep in them very quickly. Tracking tech might harm a few of these animals and possibly shorten their already short lives, but the insights learned by this may protect their population for many decades.
As a practical matter, I imagine that white collar is less dangerous than the coloured tags which totally defeat their winter camo. (This is Canada, so colour is the correct spelling!) They would probably rather the collar than those tags be so easily seen by predators.
I doubt this will make you feel better but perhaps it will provide context. This scientific team tagged 28 hares.
In most parts of Alaska, they have no bag limit on arctic hare, which are an abundant and renewable resource. This means it is legal for a hunter to go out and shoot 28 hares in a day.
Without proper studying, there is no way to properly gauge their “welfare.” So yes, the welfare of the Artic hare as a whole is more important than the inconvenience that a collar and ear tags provide to individual members of the species.
As a practical matter, I imagine that white collar is less dangerous than the coloured tags which totally defeat their winter camo. (This is Canada, so colour is the correct spelling!) They would probably rather the collar than those tags be so easily seen by predators.