AGM's are more vibration and shock resistant to a point but a well built flooded cell jar made correctly is as well and a flooded cell 'maintenance free jar also catches the airborne (gassed off) electrolyte and returns it to the individual cells but some still escapes.
Far as Optima's are concerned the rate of idle discharge (no load, battery not in circuit is the same as a conventional flooded cell battery and that is negligible. I cannot justify the additional cost of them, especially when Johnson Controls move most of their production of them to Mexico from Waterville, Ohio to cut production costs but increased the retail cost.
Far as I'm concerned, Optima AGM's are over priced and I'll never own one. If I want an advanced design battery, I'll buy (and have bought) a Hawker Odyssey sealed battery instead. Your Optima is incapable of operating upside down, the Hawker can be mounted in any position and it's 100% sealed too.
Not sure why I would care if my Optima can be operated upside down or not. I have no application where that is a concern. I have nothing against Odyssey batteries. Optima is what was available in the size I needed when I was shopping. Odyssey was not (They have since become more available in my area.) I would consider either brand when shopping.
Some flooded lead acid batteries are more vibration resistant than others. Both Odyssey and Optima are more vibration resistant than any of the commonly available flooded lead acid batteries used in cars and compact tractors.
If you use equipment regularly, the rate of idle discharge may seem negligible. For flooded lead acid, it's typically a few months of storage before it starts to become an issue. For a good AGM such as Odyssey or Optima it's typically a year or two. However, the concern is not just whether it starts the engine or not (though that is a big one), it's also that sulfation occurs more readily in a fully or partially discharged battery than in a fully charged one. The deeper it is discharged and left to sit in that condition, the more readily sulfation occurs. I use a battery minder with a desulfation circuit, which helps reverse this, but it's better to never let it occur in the first place. A battery with a lower internal rate of discharge will experience sulfation at a lower rate while in storage.
BTW: I grew up about 25 miles from Waterville, OH, went to high school about 8 miles from there. I've followed their progress over the years. Optima reportedly did experience some quality problems after the move, but those appear to have been resolved. Their plant in Monterrey, Mexico is state-of-the-art.
Am I happy that they moved from near my old home town? Of course not. Am I bummed that the price shot up (from $160 when I bought mine 6.5 years ago to $280 now)? Sure. That doesn't change the fact that they are good batteries. Well worth the price for me. My tractor is more reliable, I don't have to replace the battery as often, I don't have the corrosion problems I had with flooded lead acid (connection constantly corroding, had replaced battery cable end once, then the whole battery cable since it was too short to just cut off and replace the end the next time. Replaced fittings going to the oil cooler right behind the battery, and eventually had to replace that cooler - fortunately the main radiator was still usable.) For me, clearly worth it even at the higher price. When it's time to replace, I'm definitely goign with another AGM. Whether that is Optima or Odyssey depends on price, availability, and reputation at the time I'm shopping.
