Personaly, I would never waste the money on one. If I was wanting a small light weight battery and was not needed a lot of run time, yes the AGM's are ideal, but I would go with a stack cell rather than a spiral wound (like the Optima) East Penn manufactoring, who makes Deka batteries, also makes Bass Pro Shops, check out their's, they are the stacked cell.
Now, a little insight on all AGM's, Optima's are AGM batteries. AGM is assorbed glass mat, which means instead of having a free liquid electrolite, they have a thin piece of fiber material between the plates that's holding the electrolite. They can be used upside down, on their side, or on their end with only a small loss in output.
Because of the design of AGM batteries, they do not have the Amp Hour capacity for the same size battery in a flooded cell. Check out the highest Ah capacity of the Optima Blue Top 34 and you will see it's only 55Ah and Reserve minutes capacity is 120, and the price is outrageous. Look at the Group 31 for a Trojan or other good flooded cell battery and you will
Reserve Capacity: 120
• Capacity (C/20 rate): 55
This is Trojans group 31 AGM
http://www.trojanbatteryre.com/PDF/datasheets/31AGM_Trojan_Data_Sheets.pdf
Look at a similar Group 31 like the Trojan SSC225 and you will about 120Ah and 225 Reserve capacity for a lot less money. This is about twice the battery as the Optima Blue and less money.
It does not matter what kind of battery of it is, the Reserve Capacity or Ah capacity is going to determine how long your trolling motor runs. The construction of the battery has nothing to do with that.
AGM's when charged with a good AGM charger will give you a higher cycle count, and the fact they can be installed in any position is about the only good thing they have going. Oh, and they are light, but this is because they don't have the capacity the heavier batteries have.