You have heard incorrectly. The hybrid Highlander has not been in production for 5 years so there is no 5 year historical evidence yet.
There are 2 different generations of the Prius. The current generation Prius and hybrid Highlander use the same technology, although an all wheel drive Highlander has an extra electric motor.
I spoke with the service manager at a large Toyota dealer, he said that the Prius (both generations) have been very reliable. They have not done any battery replacements at their dealership yet.
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