I will concede that I do use two amps Everytime I gig though haha...but one's a 15w Vox. I'm all for more amps and bi-amping, etc. But since we already help move a bunch of stuff to and from shows, I would wanna limit the big poopie.
The biggest thing about having a clean amp and a dirty amp is how you can get a variety of sounds. I wouldn't be surprised if you could do that with a blend pedal though. And nothing beats a tube amp cranked. Oh man the fullness, sag, and expression you get!
I don't mind moving gear. As the band's gearhead I put a lot of thought/effort into our sound, which has produced a lot of good feedback and gives us an advantage against our competition.
The big problem I've had with blend pedals is that I can't seem to get the sound I'm looking for. It's always too much or too little, the settings that work in one situation sound terrible in another and if they sound good through the amp I don't like the way they hit the DI (and vice versa). The one pedal that has worked well oddly enough is the BDDI, but I haven't worked with it enough live to feel fully comfortable with it. I'd like to be able to take the time to dial it in through a PA with a soundman providing feedback so I have an idea of what's going to FOH, but that's a luxury I haven't had yet.
I've done a little bit of experimenting with two bass amps and two amps make it very easy to blend, and I can dial in each amp to sound good together. I can also hit the dirty amp with distortion or fuzz and know that the clean amp is staying clean with a consistent volume.
I know I can accomplish a lot of this with a clean DI and a mic on the cab with the soundman controlling the blend... but then I loose the punch/clarity on stage. Plus, we do a lot of gigs in venues where the PA is underpowered and Vox/Kick only.