One turntable with two arms, or two turntables with one each - which would you prefer?

I have two tables set up at the moment and a couple more that...well anyway.  One of mine is stereo and the other is mono, which if you have room for it and the need is the most convenient option IMHO.  Two arms on one TT is awkward for me to use because the arm along the back is difficult for me to reach/use/cue.   That is me.  I use one phono stage with two inputs and two SUTs.  Part of that is just due to practical considerations of space and money.  To the issue of need, as a jazz collector, at least in my case, a lot of my records are mono.  I mono cartridge definitely outperforms a switch on the preamp and having a mono rig hooked up and ready to go at all times is a life saver as fas as I am concerned.

I've been looking at the Acoustand tonearm pods, which would let me add a second arm to one or both my SME Model 10 tables. I have a spare SME M10 arm, and could get an M2-9 for a fourth arm. My phono amp supports up to five inputs. I know, it's crazy, but just imagine having four cartridges on the go at once! Talk about spoiled for choice.

The way I'm going to do it is keep my current 1200GR for 78's and a newer, higher-end table for everyday listening. 

If you enjoy the “art” of turntables and tonearms go for many.  I did that at one time and had 4 TT’s and 5 tonearms.  I enjoyed the mechanisms of different arms and experiencing the sound differences of different turntables.  But later I scaled down to one TT with two arms for my main system.  One with a stereo cart and the other with mono.  I play a lot of mono Jazz lp’s and love the way it sounds on my mono setup.  Have fun

It depends a lot on the space available, I have several chains and turntables both with two arms and turntables with one arm, now I am preparing a plinth for the 3-arm victor TT 801.
For phono preamps I prefer phono preamps with multiple inputs.