um.. ok. wait.
yea, they sound different. like more different than you think. they both are pretty useful.
if you are looking at them in terms of strict fidelity, software plug-ins offer great price/performance. so they work well for invisible compression/limiting, eqs can be nice as well. plug ins also seem to do well for EXTREME effects. effects that seem really top level... like if you want to run the entire mix thru a flanger. you dont really hear much BETWEEN a plug in and the sound. which has its uses.
if you are looking at color, outboard works pretty well for that. outboard gear tends to give you more "information" in sort of a strict mathmatical sense. you hear the effect, you hear the amp stages, you hear all that other stuff. its complex, dynamic, chaotic. which is cool cause you can use that to locate that effect in some sort of aural imagined space.
outboard gear tends to be more "designed" as well. like tweaked here and there to get you closer to an overall sound ideal, as opposed to just giving you a strict effect. like really nice outboard gear will give you a sweet sounding ampstage at the output, or maybe a nice thick sounding transformer, or something like that.
also, factor in that the different interfaces produce in YOU very different work habits. the tactile/visual connection between box with knobs and human is different from the computer/human connection. so, you will HEAR things differently, you will work differently.
oh and artifacts... plug in artifacts are VERY different from analog artifacts. these things are important too. digital artifacts can be more obtrusive. again, they sound more "top level" to me. struggling analog gear in a mix kinda moves to the back of a mix whereas struggling digital stuff moves to the front, at least to my ears. so digital plug ins are useful for throwing things out front, like really far out front. like so far out front that you could trick listeners into thinking that their stereos are broken.
here is another way i look at it, in terms of aural soundscape. you have these levels in your recording: (with lots of grey in between)
1. room events. what is happening "in the room" with the musicians.
2. mix levels. what is happening "at the board"
3. recorder/recording medium level. what is happening "on the face of the medium".
all the events on your recording on playback fall somewhere in there. digital is very good at getting you closer to number 3. analog is good at moving things to lower numbers.
so during mixing, you can exploit this soundscape. if you want something to really pop out, even at low volumes... some bitreduction plug in will absolutely PASTE that element to the front of the mix (an extreme example).
if you have something you want to throw back, like a software synth that just sounds like it comes from another planet from the rest of the recording, run it through a guitar pedal. or if you really want to send it WAY back, amp it and mic the amp.
so, you know, use both and have fun. boy that was like a rant. or sometin
Well in college right now I'm being trained in Pro tools, so I figured it'd be the best route for me to take. Especially like you said, it's becoming the standard. 
