It is still best to mic amps, but emulators would still work for some not however for analog tone freaks... It shouldn't mess the tone if properly set, technology now has advanced to quite a level that emulation may be considered to be acceptable.

Keeping in mind that the cones still plays an important role in sound shaping, plus the micing techniques which affects the sound you get, the cab emu may not have the range of that of manual micing and the sound that you have in mind. If your cabs are not some exotic stuff miced with paranoia, I would use an emulator... lesser hassle to get a constant tone everytime, but i have a dislike for digital when it comes to guitar =x

There is nothing wrong with your concept of recording guitar to the amplifier head straight to the mixing board. That sound however will not be particularly gratifying the way you recorded it in your mix. Might I suggest that if you record the guitar that way, you'll definitely want to use some of the many available guitar emulator plug-ins in software? Conversely, you don't need any sinkin' plug-ins if you back feed the track out to a guitar amplifier and re-mic that in numerous different ways to numerous other different tracks within your DAW. You can truly go nuts to obtain huge and different guitar sounds after the fact but keep in mind though, if the guitarists like feedback effects, you won't be able to obtain that. For that sound, the guitarists absolutely has to utilize his amplifier that his guitar is plugged into. So you're recording technique is not a be-all and all for recording guitar, just another flavor of many.

Baskin Robbins 31 guitar flavors
Ms. Remy Ann David

THe THD Hot Plate was designed specificaly to let the player take the speaker output of the amp head to a recorder or mixer. Is it identical to the sound a "real" cabinet would present to a SM57 stuck in its face? NO,
but this approach is in many cases much more desireable than a cranked cabinet is. The THD is available in different models based on the speaker impedance that the amp head wants to "see". You must be very specific and careful with that. This isn't something that you just pop between any ol' amp and cab rig. But given a particular situation (like apartment living, babies down the hall, freaked out cats, and a pissy spouse), this is a good alternative. Just remember that if this is amp has a tube output section, that cranking it up through ANYTHING (cab or Hot Plate or Power Brake,etc) will eat up those power tubes much faster than if they weren't cranked. The THD is one of several variations out there, but Andy Marshall knows his stuff and THD gear rocks! BTW, using a Hot Plate also lets you insert effects AFTER the head, on its way to the board. Adding, say, digital reverb AFTER the saturation of the amps' ouput sounds totally different than running a reverb between the guitar and the head. Pretty neat.