I assume by "integrated" you just mean low-latency? Is there any reason a USB or firewire interface couldn't have latency as low as PT hardware? What is the lowest available latency on PT and the best available firewire (or USB)? Logic's lowest buffer is 32 samples, seems like pretty low latency as far as I can tell. What is the limiting factor on native systems, is there some reason latency can't be any lower? And "through plugins" you're going to have latency even with Pro Tools, with some of the beefier plugs you'll probably have more than a couple MS.
If you've ever used a PT HD system, you'll know what I'm about to describe.
Using an HD system (either with PT software, or using another host like Logic or DP) is like using a tape machine: everything feels instantanious. When you use Logic or any other native DAW, there is a slight hiccup on everything; starting playback, record-enable...everything. You don't notice it until you fire up an HD system and then you are amazed at how everything just works so fluidly.
But the real benefit of an HD system is the low latency. Yes, Logic can operate at 32 samples. 32 samples gives a total latency of about 1.5ms (in plus out) at 44.1kHz. BUT, whether you can get 32 samples to work with your specific soundcard is another thing. With some PCI-based soundcards, you can do this, but once you start adding the plug-ins, they all introduce latency on top of this (the system compromises latency to run the plug without clicks and pops in the audio...in PT, latency is never compromised). Add to that the latency due to the AD/DA conversion, and you can easily start to get into the multi-ms range, which is unacceptable because it kills the real-time nature of audio. For top-notch performances, you've got to keep latency at around 2-3ms, ROUND TRIP; that is from the source (mic, guitar, whatever), through the AD converter, into the DAW, through any plugins, through the DA converter. PT HD systems guarantee that you can run up to 160+ tracks at this level of latency, through plug-ins (!!!), without any stress on the host computer.
Until now, 32 sample operation hasn't been possible on native DAWs because, despite all the power of modern computers, that power is going to run ever more complex plugs; as you add the next convolution reverb, you add latency. For a typical Firewire-based interface, you'll be lucky if you get solid, stable operation at 64 samples (which is, in reality, 64 + 64 = 128 samples). At 44.1, that's 3ms of latency right off the bat. You might think that's not so much, but your converters are going to add about 1ms each or so (total = 5ms), and if you're monitoring through plugins like Guitar Rig, or Space Designer, or Altiverb, you're going to add even more latency.
This is all avoided, of course, if you don't monitor through any plug-ins. Then you're just dealing with the interface and driver latency, which can be a very useable 4-5ms; still about double that of an HD rig, but about the equivalent of standing 4-5 feet from a speaker. All-in-all, not too shabby, right? Except, with the HD rig, you can have 2ms through plug-ins!!! Read that again. Want to have your vocalist monitor through a nice reverb, delay, and compressor? Go ahead; you can do it, and not throw off their timing with latency. Yes, some of the beefier plugs may introduce a little latency, but the effects will be far less than on a native DAW because everything about an HD system is tailored to keeping latency low. You can also do this in a native DAW in one of two ways: direct monitoring through an analog console, in which case you've got virtually no latency but also no effects for the vocalist (well, you could use outboard), or monitor through the DAW, in which case you've got the effects, but you've got several additional ms of latency.
All in all, until now, it hasn't been possible to get VERY low latencies in native DAWs. You might be ok with working with even 10-15ms of latency, and many people use native DAWs at 256 sample buffers (256 in + 256 out = 512 samples = 11ms at 44.1kHz) and are quite happy. But for people who need the ultimate in low-latency performance, and who NEED to track with plug-ins, native DAWs don't cut it.
BUT, Apogee and Apple have developed the Symphony system that lets you track at 1.6ms ROUND-TRIP latency, with plug-ins!!! This is really a breakthrough, and is the first time a native DAW has challenged a PT system. I'll say it again, it's not that HD systems have more power than native systems (a dual dual-core 3.0GHz Mac Pro is many times more powerful than an HD system); but the HD system always operates at low latency. When you get to be a power user, THAT is what matters; not a new fancy reverb or compressor.
HD systems have been the closest thing, in terms of latency and ease of use, to an SSL hooked up to a Studer 2" and top-notch outboard; the latency of that system is next to nothing, because you're just pushing electrons around. You've got the minimal latency of any DSP you're using, but for the most part, you're very close to zero latency. Native systems haven't come close to this...until now.
