I'm quite familiar with the SVT/Ampeg sound and have had the Tech 21 BDDI, VT Bass v2 and VTDI, the Broughton SV-Pre, and the SCR-DI. FWIW, I like a little hair on the tone here and there, but rarely use anything that I'd call full on overdrive. I currently use an SVT-7 Pro live and I think it's a good compromise between an SVT-like tone and size/weight.
BDDI - had this years and years ago. From memory, this one had a great "bedroom" tone, but nothing I did could get it to not disappear in a band setting. Granted, the current versions have a mid adjustment where the one that I had did not and I never cared for it then.
VT Bass v2/VTDI - These both sounded fantastically Ampeg to me. Both can get you a big fat tubey tone, something with a good grind, or go razor sharp (ouch, my earballs). They are capable of a lot of tone adjustment, so in addition to the EQ tweaking, very minor adjustments to the blend, presence, and drive knobs can go a long way and completely change the tone quickly. I think some have a difficult time adjusting these pedals because of the range of tones the pedals can produce. I even found myself - more of a set it and forget it type player - tweaking knobs more frequently than I would normally. I think these are great though, especially if you do like to tweak or have the ability to use a broad range of Ampeg-like tones.
Broughton SV-Pre - I bought this completely expecting it to be a game changer of Ampeg-like pedals for me. No doubt, it sounds really good and gives you a great older SVT-like sound. It could provide a nice grit on the tone and I loved the ability to sweep through mid frequencies from 220 to 3k. I put this one directly up against my SCR-DI, fully expecting it to be the winner and to list the SCR-DI for sale, but that didn't quite happen. Though it had been awhile since owning the VT Bass v2 and VTDI, from my recollection, the SV-Pre wasn't head and shoulders above those offerings tone-wise. If it were me, I'd actually go for a VTDI over the SV-Pre if doing it all over again.
SCR-DI - First and foremost, this thing just sounds like an Ampeg. Its controls are familiar and unlike the Sansamp pedals, I can quickly dial in my tone without feeling like I need to tweak more than I normally would. Without the Scrambler engaged, it's of course really clean, and side-by-side to the SV-Pre, the SCR-DI had a slightly fatter sound to my ears. I don't use the Scrambler at higher settings, but for adding a bit of light hair to the tone, I really like what the Scrambler offers - a nice, predictable grit that's easily adjustable. I don't think it sounds bad at higher settings, but it's just not my thing. With the blend knob on the Scrambler, I've always been satisfied with the way the bottom end is retained when dialing in grit. My sole complaint with the Ampeg pedal has always been the lack of a mid selector switch, but even without, for my tone goals, it didn't make as big of a difference as I thought it would when put up against the SV-Pre and its adjustable mids. Ultimately, I kept the SCR-DI over the SV-Pre and haven't missed the Broughton for one second. I liked the slightly fatter tone of the SCR-DI better and when coupled with it also being a DI, having the aux in, a headphone out, and a decent sounding light overdrive I could kick in easily, it was the winner for me.
Edit: I've never used or had a newer Ampeg combo with the Scrambler, so I have no idea the differences between those and the pedal. The pedal sounds good to me for what I use it for.
