It’s not everyday a topic comes up where I feel like I could talk about it endlessly, but as one of the most vocal/resident Pano/Dio lovers on the forum, and someone who owns way more of both than I should, I do feel like somewhat of an expert on this by now lol.
I’ve written a lot about the differences but I feel like this post I made awhile back perfectly encapsulates how I feel:
With that said though, I’d say I like them both equally and use them interchangeably. Totally depends on my mood. Panorama is the OG tho and I’d recommend that as a starting point maybe. I really hate using the term soul to describe yoyos, but there is a weirdly nostalgic aura the Panorama has, dare I say soul (
), that I don’t quite feel on the Diorama, despite knowing it is probably the BETTER yoyo of the two. Maybe it’s just nostalgia from the era I grew up throwing in (late 00’s-early 2010’s), idk. You can’t go wrong with either but I say try the OG, and then try the “souped up version” later. Another small note worth mentioning - the 7075 of the Dio will be more durable than the Pano’s 6061 - I’ve got way less damage on some on my Dio’s than my Pano’s despite doing similar… things… to them. 
@OlHandyJenkins description of the Panorama vs. Diorama is my favorite I’ve read yet tho, and I couldn’t agree more with it, as it’s exactly how I feel: