Actually, I should have read your post more carefully. It's not a case of digital gear vs. analog gear. It's more a case of delay/reverb fx (use spikes for these) vs. EQs and the like.
The one sample spike is fine. You didn't mention the amplitude of the spike - I wouldn't go 0 dbfs, I'd probably shoot for -10 dbfs in case there's some gain somewhere.
I tried to make the spike as high as it would go because the output of the reverb unti(s) were barely even visible even with the spike at maximum. It seems like it's a bit shy of 0dBFS, but I couldn't draw it any higher anyways. Actually, it's that the output seems so low in comparison to a full level spike that makes me wonder if I am going about it wrong. In the end, the IRs seem to sound fine to me, but I have no way of knowing if they could be better if I don't know th proper way of doing it.
I was told that when recording digitally, to always use a spike instead of a sweep. I'm not sure why, and still wonder if there are some effects where a sweep is more appropriate. If something is a multi effect that includes some kind of EQ, I imagin a sine would be better, no? I am really curious what problems I would have usin a sine, because it seems like it would be better overall to cover every type of FX.
I also wonder if there are instances where recording mono input, even if the device has stero input is better. For instance on a flange, I am likely to catch the sweep at a different part of the cycle when recording the 2nd input. At least thats what seems like a likely result from my brief understanding of how IRs work, but I may be wrong for all I know.