Make sure you run each Pingdom test a few times to average out results!
The two things that will most likely account for your difference in results here are :
- The power and other specification of the server – the faster site is https, so may be able to use http/2; the faster site may be compressing the pages; Is your site on a low-powered shared server? Is the faster site on a dedicated server?
- The location of the server relative to your Pingdom test location – I don’t know where the 2 tested sites are located, but it will be difficult to do a decent like-for-like test if they are on different continents and the Pingdom test doesn’t reflect that.