When I've tried to improve at visual design, the hardest part was developing taste. Comparing options side-by-side and articulating why one is better is exactly how you build that skill. The aggregate rankings matter less than the act of judging.
Have you considered adding a "why did you choose this one?" prompt to collect qualitative reasoning alongside the votes?
If I don't belong to one of the markets that the landing page is trying to sell products or services to, I shouldn't be able to vote -- if I vote, I'm just polluting the dataset of what their actual potential customers think of it.
If the two landing pages being compared aren't targeting the same market of potential customers [+], it's unclear what comparing them achieves.
It's unclear if voting on a landing page in this kind of artificial setting is predictive of something more material like how often a potential customer proceeds to sign up for a demo, or pay for something, or call sales.
[+] or given a lot of these are AI landing pages, I guess they're targeting investors.
UPDATE: After trying more, found that if using the iPad with a trackpad, then a pointer "mouse over" a page zooms it, for the upper page showing a small vote button lower right of frame, but for lower page, can't see bottom of frame. Which page works to scroll seems random or neither.
OFC, iPad doesn't normally "mouse over", unless using the trackpad keyboard for it.