have you ever found yourself lacking bottom in a venue with your 410? I admittedly haven't used the 410 for that long compared to the 1210, but at my gig this past Monday, when I cranked the bass boost on my Mike Lull M5V up to close to full, I was shaking meat balls and canoli off of the tables. Older people were complaining that their fillings and hearing aids were being shook right outta their teeth and ears
It was an outdoor job in an open tent, with seating room for my guess around 200 and standing room for another 150 or so. There was no echo whatsoever. Here's my "point". The 21012 does have a lower HZ rating and a higher SPL. Even though I have played 5 or 6 string fairly exclusively for the past 15 years now, I 've always felt that tightness of the B string, not just in terms of how it "feels" to your fingers, but in tone, be it punchiness or sounding like the other strings, etc. within reason, and having a cabinet and bass where all the strings sound similar and are as close to the same volume are the keys to live sound. With all the cabinets I've ever owned, I've never had one that's been lowere than a listed 39nz low end response at whatever + or - x db's the manufacturer listed (yes this needs to be more standardized, maybe?), and never had one above 101 SPL UNTIL NOW.
I personally feel that 40HZ and a high spl gives you more versatility and less rumbling, muddiness issues live than a 35Hz high efficiency cabinet, which up until now was really rare to find. The 21012 maybe indeed have a rounder and more booty sound at the same tone settings, but I feel you can use on board the bass, the amp/preamp, or a rack or a floor mounted graphic with the 410 to get that little extra bottom end roundness, wihout giving up the punch that the 410's are likely to have more of
Again it's just an opinion as I was going through this same decision making process a month ago. The 410 is the right decision for me as I would prefer to turn down the bass boost a little and turn up the amp to be heard more easily than to increase the bottom end so much it clouds up the sound, makes it rumble around a venue, or makes the tone a little more difficult to mic up.
Again just an opinion, but a very experienced one, especially in very often playing in extremely lousy sounding venues and what one needs to do to "get over it" in those situations.
Have a good one.