Yup, "it depends"....
You can try:
Same mic, two different pre's.
Same pre, two different mics.
Two different mic through two different pre's.
Or my favorite! One mic for both. Perform both vocal and guitar at the same time!!!
The studio I work at used to only have one class A preamp, a Focusrite Red. The only would use it on EVERYTHING he could. When I used to just work in their occasionally, I found myself NOT using it that much, preferring the ART Pro sitting in the rack.
Then he got
a Drawmer 1960 pre/compressor. Nice! I found myself liking that bad boy over the ART in stuff that needed to be quite clean and VERY open sounding.
The, after I started working their 5 months ago as a staff engineer, we purchases an Oram MWS. Found myself wanting to use that bad boy like he used to use the Focusrite. I use it on as many things as I can think of. VERY nice sound, and the "Magic EQ" on it is wonderful going to tape.
After the initial "gee whiz" of the Oram, well, I find myself liking combinations of things. Hell, we have 32 tracks in the studio, so for most productions, I have more than enough tracks to play with. On acoustic guitar for example, I have been using a AT 4050 on the neck, and a AKG 414 to the left (as you face the guitar) of the soundhole. If I want a very clean, sort of sharp sounding acoustic, I run both mics to the Oram. If I want a very smooth, sort of silky sound, I run one mic to the ART Pro, and the other to the Drawmer.
For voice, many options available there! ADK TC 51. AKG 414. AT 4050 and 4033. Nuemann U87 (believe it or not, we seldom use the pair of U87's at the studio!!! They just don't have the clean, open, brilliant sound some of the other LD condensors have....such a shame of a pair of mics that cost $5k!!!). Which pre I use really depends on what I need in the sound. I could try to list all the combinations, but that would take a while.
The point is dobro is that variety is cool for sure. But, you STILL need an idea of the type of sound you are after. You still need a "production goal". EXPERIMENTATION is the key word here! Having a variety of pre's and mics means you chances of finding a combo that works are much better. But, this doesn't mean that your production can't sound top notch with less variety. Me and the owner of the studio sit around and talk a lot about what kinds of micing techniques and what gear we used for tracks on certain clients. Of course, we are always listening to the stuff. I admit, I get some very good ideas from him, and I am sure he could say the same. This helps because we both have in our minds, the memory of all these sounds, and when faced with a new client, can approach the mic/preamp/micing technique stage with a much better "guess" at the very first. This helps save the client a bit of money, and of course makes us look pretty good....
Anyway.............Good luck.
Ed