IR all the way in all cases. Having done FOH mixing one of the main problems getting a good mix is loud guitar amplifiers on stage. In many cases the FOH mix basically consisted of a mix coming out of the speakers and stage sound coming from the guitar amplifiers. Since its not the 60's and 70's anymore I see no point in having loud speakers on stage as they interfere with delivering a good FOH to the audience. And that's excluding unwanted feedback issues.
As a musician loud amplifiers on stage create a swash of noise that lead to unwanted feedback an an inability for the musicians to hear themselves. Because of that volume wars happen where musicians start turning themselves up to be heard, causing arguments with their fellow musicians. And that is excluding the fact that having to haul amps and cabs around creates additional logistical problems for the band. Not to mention that amps and cabs are heavy, and since few of us can afford to hire roadies to haul them around for us, why subject ourselves to having to haul them around.
And for what really? That special sound that nobody in the audience will notice anyway? In my experience just when you thought your tone sounded the worst its ever been, that's when you will get complimented over it the most. The Universe has a perverse sense of humor in that regard.
As for recording, I'm willing to admit that there might be merit in having the best possible sound on your recording. If you were in a professional studio that is, with professional sound proofing. If recording at home, either invest in building or buying a good isolation box, or learn to make IR's work for you as well.