Lithium Battery Question (School me on Group Size and Power Output)

[R1Peacock]

I feel dumb as hell asking this question but before I drop $$$$ I want to make sure I’m understanding what I am reading.

I’m looking into upgrading to Lithium Batteries for my Champion 198 Elite this season (just for trolling motor, graphs, lights, livewells, etc. — no cranking). It seems the technology is increasing pretty quick and the size of these batteries is getting smaller (but they look to have the same power output). If a Group 24 battery is 12v 100Ah with 1280Wh and a Group 31 battery is the same —- What’s the sense in getting a Group 31? — am I missing something???? I’ve even seen a few claim to have a Group 22 now that packs the same power output. I’ve always used Group 31 AGMs in my boat and probably had 200 pounds in batteries alone. I’m looking to cutdown on weight and using smaller batteries would open up space for other add-ons like PowerPole Pumps. I’m also looking to build out my son’s Kayak so saving size and weight really matters.

[ZO6]

Might be a good question for Will Prouse on YouTube. He seems very knowledgeable. I agree 100AH should be the same. But different types of cells are used in different size batteries which can require more or less space. Also particular case sizes are used in some instances because Americans understand what a gap 24 or 31 size is. some cases have space in them with foam filler for protection or "just filler." I've had the same questions as you. I tend to believe 100ah's is 100ah's until someone shows me a better way to evaluate.
Depending on your trolling motor size you should pay attention to the BMS capabilities. Initially some very cheap batteries had inadequate BMS capabilities. Not so much now but still worthy of a look. JMHO.