Dennis it's ultimately up to you, but if it was me, I'd be going for the Model II (with twin subs) as the sound dispersal - thanks to the articulated drivers - is indeed "superior" to the older models.

This is usually described as Model I having a narrower beam of sound and "hot spots" in the room sound-wise (more like a conventional PA). So simply, if you A/B the 2 systems, apparently it's like this:

Model I - Close your eyes & you can tell where the L1 is placed in the room.
Model II - Close your eyes & you cannot easily tell where the L1 is in the room, and there are no Hotspots as the music is all around you (like Love )

Just btw, we had an early gig Last Sunday and ended up in a large Club we play at often, and to our surprise the Act (Duo - 2 Guitars/Vocals/Sequencing) were using a Model I Bose (!) So for the first time we were able to sit down and watch a "Bose-Band" that wasn't us!
I found the sound to still be amazingly clear and the bottom end was great, & they only had one sub!! (it was a Country act, so they didn't need much) but still the warmth and the clarity were knockout.

The issue of the PA being Mono is non-existent for me (and certainly for all the Audiences we've played to so far!) but there HAVE been phasing issues with Yamaha Keyboards - well documented - because of the way Yamaha outputs to Mono, the actual "mono samples" are also part of the problem I believe. (You have a Roland do you not? if so, I would confidently ignore the Mono/Stereo output issue).

Also, I and many others feel running a conventional system in Mono to see how it might sound from an "L1 perspective" is comparing Apples and Oranges.
Regarding my cut n paste story above of that young DJ listening to us - I should mention he was amazed that the Bose was a Mono PA - he saw only one cable coming out of my keyboard and thought "hang on it MUST be mono" but he still couldn't "make the connection" if you know what I mean - it didn't sound like a "normal" mono PA to him. I guess it's the clarity and "sound from all around" kind of effect that the L1 (especially Model II) has that makes the whole mix sound quite "alive", to the point where Stereo/Mono is just simply a non-issue.