Someone saying that Infusion is smoother than The Smiler doesn’t have “an agenda”; it’s simply their opinion. Based on my experiences of both, I profusely disagree with that opinion, but it’s not up to me to dictate what people should and shouldn’t think.
As
@pluk has said, rides also vary to some extent. Personally, my one ride on Infusion was absolutely abysmal, and far rougher than any ride I’ve ever had on The Smiler or any other ride I’ve ever ridden, but Infusion vs The Smiler may not be the fairest comparison for me. I’ve only ever ridden Infusion once, and that was nearly 5 years ago, whereas I’ve accumulated 18 rides on The Smiler over the course of nearly 10 years, with my most recent ride being in March 2023.
Even on my last 2-day visit to Alton Towers in March, I had two pretty different rides on The Smiler. On the Saturday, I rode in a front row outer seat, and it was pretty smooth and enjoyable, it must be said. It was possibly the best ride I’ve had on it in many years! On the Sunday, I rode in a row 3 or 4 outer seat, and it was a fair amount rougher and more nauseating. If it varied even between those 2 rides, goodness knows how much it varies over numerous rides!
With that in mind, I can understand why someone might find Smiler rougher than Infusion or Grand National. I do not agree based on my experiences, but they are just that;
my experiences. Someone else’s experiences could be completely different.