Well For one they aren't called "Water Cells" so if involved in the battery end of it you wouldn't call them that they are referred to as "Wet Cell Types". They aren't filled with water they contain electrolyte. What your missing is Number 1) the factory battery really IS an AGM, not a wet cell and I've shipped those to Antarctica. And Number 2) when not working for two Indy Car race teams and one sports car team I did industrial battery applications for Fiserv (banking data backup, as in everyone's checking account) Miller Brewing Company and Strong Investments. as well as testing for various suppliers and building our own industrial cells, Tubular, Electrolyte Circulated, Flat Plate, Absorbed Glass Matt and Valve Regulated. The testing on Lithium was extensive. They are light and also fragle. I was in that business for over 20 years For serious stuff like a sled starting in the middle of nowhere like I go, I'll stick with what works. The center of gravity argument is moot. Like I said that little bit you wouldn't notice.
I never called them water cells
I said WET Cells , next sentence, (I was referring to what was in them), and the batteries we use do in fact have Electrolyte and Water in them! We use C & D Technologies "WET" type Cells as are plant back up batteries. We use Deionized water(DI)to get cell electrolyte levels back to a engineered specified level "above" cell plates due to evaporation. I am no Battery engineer, I am an Electrician who happens to maintain these battery systems as one of my many jobs I perform there. But I do talk with our Battery engineers we have on site. The main reason most facilities haven't gone to lithium is COST! Now I'm not trying to have a pissing match here with you, I've seen your stats and a lot of your involvement here. You clearly have quit a bit of knowledge and I'm grateful for what you bring here and the advise and knowledge you share.
You are correct with some of the Lithium batteries out there, "not" being up to snuff when it comes to durability. But there are some that are!
Also I just checked you are right about OUR factory batteries. They are indeed a Gel type. I brain farted on that one. I was thinking of the batteries on my Sno Scoot and my 2005 Sabercat 700, they were both WET types.
As for starting your sled in the middle of nowhere?? I would say yes I agree with you on that also, definitely use what is most reliable. But, that is why I have a pull start, that is my back up! I would say if you have a 4 -stroke(that's heavy already) or have the upper body strength of a 95 year old woman then yeah, definitely opt for the most reliable battery out there!
Now if your that worried about a dead battery in the middle of BFE, then I would suggest this nifty little jump starter I saw on Power Modz(You Tube), small, light weight and powerfull, it's actually really cool! I'll try and find you that link or the name of the company!