The old and new Reddit UIs are both bad in different ways. The new one is just bloated, the old one is not responsive and makes it hard to view images.
Couldn't tell you myself. Outside of 10-15 second unexpected intervals, I haven't used anything but old reddit since before it was old reddit, so I couldn't tell you how it is compared to the previous one.
Can 100% tell you the web-based-mobile site is pure unadulterated artificially-slowed ass.