The differences come down to two different design paths.
The JOR uses the Dynaco circuit. It's a fixed (adjustable) bias amplifier. The i35 uses the Mullard long-tail pair circuit, with cathode (auto) bias. Apart from the aforementioned front-end, fixed bias amplifiers generally more produce a more immediate and incisive character, whereas cathode bias can sound more liquid and lush.
Despite Jadis' traditional pricing structure, I don't feel one is necessarily superior to the other. I own the JOR, DA30 (Mullard w/cathode bias), and DA60(also Mullard w/cathode bias), and appreciate the characteristics of each. As always, it comes down to personal preference.
Personally, before "upgrading", I'd give the JOR another look/listen with the type of tubes that suit you best, as well as biasing the amplifier at a hotter level than the far too conservative factory settings. I think you might discover the JOR produces some of the most sublime midrange in the industry.
