No box of transistors is gonna nail the sound (and more importantly, the feel) of a full tube amp, they are just using different iterations of the same basic Ampeg preamp building blocks into some sort of basic overdrive circuit. I know this isn’t what you want to hear, but really the only way to know what will work for you is to test it with your own ears/hands/gear. I played SVTs (old and modern) for years and definitely the basic tonal vibe is there in the Super 300, certainly moreso to my ears than the Sansamp VT (or any of the Tech 21 products) or many of the SVT plugins I have played through. Still everyone is attracted to different aspects of what an SVT can do, so for certain uses different options will have advantages over others. I do find the Super 300 to tend more towards the “SVT CL with preamp Gain pushed” type of sound, but I’d expect that to a degree as the original circuit just didn’t get this gritty on its own in most reasonable use cases. I’ve yet to try any emulation of an SVT that gives that same feel of endless headroom that the real thing can (a result of pleasant soft-clipping combined with the reserves of large transformers), but that feel part is why people still buy tube amps!
I can’t speak to the Broughton or other more pricey options (like the Origin Effects Super Vintage, which is the new cool SVT pedal on the block), but the Super 300 fills my occasional need for that Ampeg sound well enough that I don’t really have any GAS for other options (it generally isn’t the sound I want, which is why I moved on from those amps a long time ago but sometimes it is definitely a good familiar option to have on hand). My biggest critique is how quick the Gain breaks up (even my lowest output bass is pretty gritty by 10 o’clock on the Gain knob), but apparently this is something improved by swapping an audio-taper pot in for the stock linear pot which isn’t a big deal (just not something I’ve gotten around to yet).