I think it's a) a matter of personal taste, and b) experience in discovering what cabinet combinations work well in transition. Consider that in the "real world", you have guys that use pedals or change channels to gain stage (which keeps the amp/speaker combination the same). You also have guys who might have 3 different amps on stage (clean, crunch, lead) because they like the feel/response of the different amps. You have guys that shape their tone via volume knobs and split pots. And then you have some guys that do all of the above.
Me personally, I do all of the above. I have 5 basic patches:
1) Brownface Clean with 2 1x12 cab sims
2) Mr. Z. (hint of breakup) with 2 1x12 cab sims
3) CAE (mid gainy) with a 1x12 and 2x12 cab sims
4) JCM 800 with 2 4x12 cab sims
5) Rectifier with 2 4x12 cab sims
I have 2 overdrives in each patch as well as PEQ boosts etc. So I can go from clean-dirty and everywhere in between in several different ways. (I also have p-rails on my main guitar which give me single, p-90, parallel-hum and series-hum pup options).
One of the first things I did when I decided to take this approach was to not only do volume-leveling between the 5 patches, but also do EQ LEVELING. For example, typically a Rectifier has a modern sounding scooped mid-range vibe going on (whereas the CAE and JCM 800 are more in the upper-mid range family of amps). Knowing this, I DON'T use a 4x12 v30 cab with the Rectifier because it's going to suck even more of my mid-range away. In fact, after the cab, I boost the upper-mid frequencies with a PEQ block so it's not as radically different sounding than the JCM. The guys at the board always appreciate this. During sound checks, the patches are close enough that there is no MAJOR EQ differences when I switch from one to another. And when I play, the 800 still sounds and feels like an 800 and the Rectifier still sounds and feels like a Rectifier. It's just not quite as scooped (which also keeps the 'vintage' guitar players from complaining about the "angry swarm of bees" sound).
On the clean side, I love playing with the neck+bridge setting. Obviously this gives me way more low-end, so I choose cabs that aren't overly bassy to compensate.
My suggestion to you is to try to come up with different cab combinations that are SIMILAR in terms of EQ. The goal is to go from a 1x12 to a 4x12 WITHOUT the extreme EQ variances.
Hope this helps!
-AL
