uuuhhh... Weird question?
MIDI is just a control message sent to originally just hardware, but nowadays obviously VST effects and instruments as well.
A sample is just a pre-recorded sound source, a reproductive sound source then, as opposed to the oscillators in an analog synth which are a generative sound source.
Both can be triggered and manipulated by MIDI, which is just a protocol for that. Like WAV or MP3 is a way of transmitting recorded sounds.
But those lines are completely blurred, and have been for a long time:
-Take a wavetable synthesizer that uses samples as oscillators. Vintage drum machines that were sample based, or hybrids like the TR-909.
That stuff has been around since the 80s.
-What to make of any synth that's a digital plug-in?
-Or granular synthesis? Again, using samples as a generative source, but at a much more euh.. granular level. Here it becomes impossible to tell,
and irrelevant, whether it's sampling or synthesis. If you're using it to stretch a sample, then it's more like sampling, but if you're using the grains
of the sample in completely different ways, it's more like synthesis.
MIDI is still just a communication protocol. Like suppose you load a mess of drum samples into Battery to make a track. You'll be triggering those
samples with MIDI notes. The sounds it uses are all samples, but they can be samples of anything.... One thing I like to do is make a bunch of drum sounds with a synthesizer and just
save them out separately for later use and further manipulation. There's things you can do with audio-editing you can't do with MIDI and vice versa. The huge building pads at the end of my last track
could only be done with a synth driven by MIDI. It's same notes over and over, but the changes in the sound are achieved by playing with the (amazing) filters on my synth which I actually recorded in by hand.
But then, since it's coming from outside hardware I had to record it to a wav file.. which in essence is just a very long sample sitting in my library now.. ready to be used as such.
So... summing up: interpreting your question as either 'samples vs. synthesizing drums' or 'automating MIDI vs. Audio-editing'... I say, where do you draw the lines? Can you even tell the difference?
Like in my last track, there's samples and synthesis going on in equal measures, but which is which? Just the kick alone is a combination of 3 sounds, 2 came from Maschine's Drumsynth, the other was a sample from a library.
I recorded those together and treated them as one from there on. So it's a sample, from a virtual synthesizer though... and it's never looped, so every single kick you hear is triggered by a single MIDI note.
Just for the crazy, I then took that kick and stretched the hell out of it, combined it with synth sounds and so it also forms the basis for that clicky bass sound going on throughout.
There's no way you can tell, as a listener, how that all fits together.
The only reason to make one choice over the other, is a creative decision. I want to achieve this sound, and this is the easiest or nicest way to get it. I always place results over process.
Like maybe a reason to grab the hardware TR-808 over samples, even though it's not as convenient, is because the TR's circuits make it slightly random... every clap is gonna come out ever so slightly different.
If I was building a minimal techno track and I want that raw clap to be a prominent fixture, then that slight randomness is perfect because it'll avoid that static, programmed repetition and just sound more lively.
If I was using it as part of giant drumkit in this really epic, massive sounding track with drums everywhere... then who gives a fuck about "But but.. it's a real hardware 808!!!"?