Consider warranty as well. Batteries Plus has their 31AGM Marine battery made by Northstar and has a 4 year free replacement warranty. I believe Northstar is only 3 years on theirs. Not sure on Odyssey.
X2 power is made by northstar with same specs that northstar batter has. I purchased mine from batteries plus. they also have 10 percent off right now and almost always. Best battery I have ever owned. I run power poles, solix 12, kicker stereo and have yet to see it drop below 12.2 volts. Also paid close to 400 bucks but worth every penny. They do provide 48 month warranty.