Is Shinkansen Price on Klook reliable?

I’m trying to buy Shinkansen ticket for my Japan Trip and I’m looking on both Klook and SmartEX App. What I can’t decide on is that the ticket price on Klook is way cheaper than the ones on SmartEX, like more than half price. Those are literally same tickets of First Class of the same line on the same schedule. (I’ve also check with exchange rate and everything). Obviously, I want to choose Klook price but I’m afraid there might be some underlying issues that I might have missed. Any ideas or your experience, please?