My thoughts:
Fractal was actually kind of disappointing to me. Had to go way more extreme with settings and even then I couldn’t really get the low end as hefty/lively, nor the aggressive upper mids quite the same. It’s close enough but the areas where it was falling short are the specific things I’m looking for in a decent 5150
Helix. Was quite amusing - I’d saved my own default settings so loading the amp up was already 85% of the way there. I dialled the mids a bit higher than normal so matching that closed the gap a lot. It still sort of sounds like Helix but I think it’s a solid model and I’m actually surprised it gets a bad reputation (got a feeling it’s almost entirely down to its stock settings). Settings on this were closest to my real amp FWIW.
Nolly. Pretty solid, couldn’t quite nail every aspect, somewhat like the Fractal model (albeit with less extreme settings required). It has aspects I like more than Helix in the gain character/fizzy stuff. Low end is a little flat. I tend to use it over Helix because of the GUI and gain character.
Amplitube 5. It’s overlooked and better than people realise, but again, dreadful default settings. I prefer all others besides Genome to this one. If you already have it, it’s worth a go though.
STL Amphub. Feels quite nice to play. Had to exaggerate settings a lot to get close. It’s fine but I overlook it for the most part.
STL Middleton. I prefer this one to amphub but they’re 95% the same. Just like dialling it in more I guess. Still had to exaggerate things, still couldn’t really get the low end heft and dynamics feeling as good.
Genome. Didn’t like this one. It sounded and felt weird and it’s why I dived into this comparison again. Couldn’t really dial it in any closer, it’s kind of stuffy and stiff and bloated. It’s the only one I wouldn’t feel comfortable using for achieving a 5150 sound.
Real amp took literally 3 seconds to dial in. All the magic stuff is just inherently there. I know the tactile aspect and familiarity is a factor but you don’t have to do anything weird to achieve the goods. All of the emulations require some amount of work to approximate the good stuff and none really achieved it. They’re impressive and close, and yet also there’s a noticeable gap both in tone and the overall experience in getting there.