While I am totally for recording a guitar amp with a microphone, which is what I always do, the idea that all the greatest guitar recordings were done that way is not exactly true. There are PLENTY of soul and funk records where the guitar was plugged directly into the line-in of the console and recorded that way. There are also many instances where a distortion pedal was plugged in the same way in a lot of older records for raspy distortion such as on Rodriguez's Cold Fact. It was not uncommon. No cabinet or amp modeling there and it sounded great in that material.
Saying that there are a lot of variables at play when recording live guitar with a mic and those include a potentially problematic room which can make getting consistent tone pretty difficult if there are dips and humps in its frequency response, particularly when playing loud enough to excite the room. Ironically you have to really push
a tube amp to get a good sound out of it. Then you have to place the mic - the RIGHT mic - correctly to achieve the sound you want. Then there's the matter of having the right amp at your disposal to supply the tone you're after. The list goes on. Recording electric guitar competently is not just a simple matter of mic->amp->guitar. However, as we all know, once you get it right, there's just something about recording a great guitar played by a great player with the right mic in the right position in the right room. It can be magical and trumps an amp-sim every time.
The advantages, on the other hand, of using a good amp-sim are many. No inconsistent room tone to deal with. No mics. Vast tonal variety. Saved settings for total recall. There's something to be said for just plugging in and getting going on what's important: being inspired and getting the vibe of playing. Given that amp-sims these days like the Kemper modeling amp,
AxeFX and others are getting so good, it's no wonder people are turning to their convenience. I personally have always thought Line 6 was vastly underrated because of the stigma of the clownfucking aspect. People are skeptical of digital, especially the luddites who cling to their '57 Les Pauls and precious JTM45 originals.
At the end of the day it depends on what your goal is. Amp sims may work for some material and may not for others. Line 6 is good option and they are the pioneers of amp modeling. FWIW, I know for a FACT from touring with these bands that Goldfinger and Mushuggah used
Pod Pro's instead of amplifiers on all of their lives shows. No amps at all besides dummy amps. Weezer also did it. In my opinion, the prowess of the player is far more important than the nuances between real vs. digitally modeled amps.
My 2c.
Cheers
