I would guess there aren’t many responses because it really is a personal decision based on your needs and preferences. But I’ll explain why I went the direction I did.
I previously used a typical rack interface and it was a great interface, but I needed more inputs and in the end chose the SL32 Series III. Technically, the previous interface was supposed to be the superior sounding since it has 96 kHz capabilities and the SL32 is max 48 kHz. However, I am in a home studio and could not tell any difference in sound quality. In fact, the SL32 sounds absolutely amazing in my opinion. I went through the same dilemma as all of you and considered adding more preamps and getting a Faderport 16, but am very happy I went with the SL32 instead. Since sound quality was the biggest advantage in the interface + additional preamps + Faderport column, I was very happy (and relieved) when I heard how great the SL32 sounded.
The reasons I am happy I went the StudioLive route off the top of my head:
1. I have more preamps than I even need and can leave instruments and mics plugged in ready to go and I have them labeled on the mixer scribble strips and set up Studio One to match so setting up all channels to record takes seconds. On the SL32, 16 of those inputs are combo jacks so I can plug synths directly in and don’t need to DI anything except guitar and bass if I want to record a dry signal for reamp options later.
2. I have the main outs going to powered PA speakers and can turn on the mixer and practice synth or whatever without turning on the computer at all. This should be 1 because it’s a big enough deal for my setup to have been the only advantage I needed to make this decision for me. When thinking about the interface route, I was trying to think of some workaround and everything seemed like it would be a pain and cost extra $.
3. I have the monitor outputs going to studio monitors so I can easily switch to DAW/mixing mode without unplugging anything.
4. I have freakin’ 16 monitor mixes (or it looks like 10 on the SL16)! These can be used all kinds of creative ways-individual headphone mixes, monitor mixes, hardware FX sends, or my favorite sending keyboards to an amp so I can record direct on the keyboard channels while recording the amp at the same time on another track! Sure, you could also reamp, but think of the time this alone saves.
5. The EQ and Comps on the fat channel are not only fantastic, they integrate so well into Studio One it’s crazy! There is a video on Presonus’ youtube channel explaining it where you can see how well thought out the implementation is. There are also reverb and delay onboard, but neither are very good so I’d only consider that an advantage for convenience during practice or live work. For recording/mixing I would (and do) rely on some higher quality plugins or use outboard gear through the AUX returns. Or if you’re broke after buying this mixer. :) The range and quality of the EQs and Comps however combined with the Studio One integration has met all my needs for those duties.
6. It’s USB and I don’t have Thunderbolt ports, so that would’ve been a whole other headache/expense.
7. Switching between the live mixer side and DAW control is the push of the button. I guess this isn’t a fair comparison since with the interface route there is no live mixer side!
Really for me, everything just makes perfect sense, is super easy to use, and I have all the functionality I need for both practice and recording, so it was the perfect solution for me. I couldn’t be happier. The combination of the sound, convenience and functionality at this price point is nothing short of a miracle for my needs. Having said all that, if you are someone who records one instrument at a time, uses a lot of software instruments and mainly just track vocals, are an acoustic band where you throw up 4 mics and don’t need a bunch of line level inputs, live in an apartment where you have to be quiet so don’t need the live mixer functionality, just do voiceover work, or any number of reasons where you don’t feel you’d need the functionality that I listed above, the StudioLive series III is probably overkill. Also, if you feel you need a higher sample rate than 48 kHz, this should make the decision for you (I personally would need to spend way more than I have or could justify on studio treatment, expensive mics and pro monitors before I think I'd be able to benefit from a higher sample rate). You could technically track on a different interface and still mix down on the StudioLive, but you would lose so much functionality that makes it great, it seems like a waste to me. Anyway, that’s my 2 cents. I personally feel like the StudioLive mixers are a crazy bargain for what you get and the Faderport is crazy overpriced for what you get. But these are all tools and it depends on your workflow and needs.