Put a lot of amps into the same cab and they will have way more similarities than you'd think.
Nothing new, but If anything, this is possibly my biggest takeway of all my endeavours in modeling land.
I kinda knew how cabs would make a difference before IRs came up, I also knew how mics would make a lot of a difference, but I still remember when I finally had a computer capable of running lots of IRs at the same time (2007 Macbook with Logic's Space Designer) and heard about the IR frenzy, so I started grabbing my guitar signal with a DI box inserted in the speaker path and got the RedWirez teaser pack and their Big Box shortly after.
That was a mindblowing experience because the general shape of the guitar tone could be manipulated in an amount of ways I could hardly believe (way more than any regular EQ-ing could do).
And it's been especially noticeable on overdriven tones. I could almost manage to make my dirt stompboxes sound the same even if IRs are sitting behind what we typically think of as being the main tone shaping stage (which it still is, of course...). Or rather: Some IRs would make the differences of the core tone stand out much more whereas others would rather "mask" them. And even more astonishing: All that was happening well within whatever "totally acceptable" range, so I wasn't comparing a 3.5" radio speaker with a 4x12 but rather, say, just 2 variations of a Celestion.
As said, nothing new by now anymore, but if there ever was an eye opener related to modeling, for me it's gotta be that experience.