A tent will do everything a bivy can do. But a bivy can't do everything a tent can do. The advantage of the bivy is that it's usually lighter and simpler. But believe me, you won't care about that when it's raining buckets and/or the bugs are swarming.

Go with the tent.
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If you only travel on sunny days you will never reach your destination.*

* May not apply at certain latitudes in Canada and elsewhere.