It's a loaded question and to you the user they should be equal if both 1st stages are tuned right.
I would just pick whichever one makes you happy to dive with or flash around.
From a service technician standpoint however, a current edition (9000Pro model) Maximus will be able to be tuned to a wider range of easy breathe to hard breath. The 109 takes more of a PITA to get it to do that; sometimes with certain individuals you can't get it to breath light enough without it freeflowing. So that's what the new tech really has improved on. Nothing really noticed by the end user; lots noticed by the technician.
My 109's I can't for the life of me get them below 1.4 inches of water cracking pressure. Now 1.4 is perfectly normal and good but I'm anal about having my regs breath at a 1.0-1.2 inch of water. So I have to put up with that.
The newer tech regs often allows you more adjustment points to change the setpoints for your reg. Sherwood allows adjustment of the orifice and fine tuning poppet spring tension. With the 109 you only have the orifice adjustment and bending the demand lever, which the latter is impossible to fine tune to your naked eye.
So for instance with a Maximus, I can hit any range of setpoints easily and creep gradually from easy breathe to hard breathing. With the 109, I would be jumping gaps from easy breath, moderate, hard breathing. There's not an even spectrum of fine tune adjustment; but when you do get it right it's much more satisfying.
For moisture retention though, I would argue the 109 is better than the Maximus. More metal means greater surface area to condense. The Maximus only have the metal fins and the metal barrel to condense, so far less surface area.
Now if you're talking the older 7000 series Sherwoods (the ones where the 1st stage doesn't do a 90 bend and just comes straight from the tank valve). Then those are exactly equal to the 109 in terms of tuning.
