Leisure battery choice used to be simple - lead-acid, or the slightly better AGM (Absorbed Glass Mat) version of the same basic chemistry. Lithium (LiFePO4) batteries have changed that, but they're not automatically the right choice for everyone.
Usable capacity
This is the headline difference. An AGM battery shouldn't regularly be discharged below about 50% without shortening its lifespan - so a '100Ah' AGM battery gives you roughly 50Ah of genuinely usable, healthy capacity. A LiFePO4 battery of the same rated size can typically be used down to 10-20% remaining without meaningful damage, giving you close to double the real-world usable power from the same rated size.
Charging speed
LiFePO4 batteries accept charge far faster than AGM, meaning shorter driving times or smaller solar setups can still get you to a full charge. This particularly suits anyone doing shorter trips who wants to top up quickly rather than needing hours of driving or sunshine.
Weight
A LiFePO4 battery typically weighs around half that of an equivalent-capacity AGM battery - a genuine consideration if you're close to your motorhome's payload limit.
Cold weather
Standard LiFePO4 cells shouldn't be charged below freezing (though many now include a built-in heating element or protection circuit that handles this automatically) - worth checking on any battery you're considering if you plan on winter trips.
Cost
This is the real trade-off. LiFePO4 batteries typically cost several times more than an equivalent AGM battery upfront, though many owners find the extra usable capacity, faster charging and much longer expected lifespan makes the sums work out over several years of ownership.
The honest summary
If you camp mostly on hook-up or drive frequently enough to keep an AGM battery topped up, the extra cost of lithium may not pay for itself. If you spend a lot of time off-grid and want to actually use the capacity you're paying for, lithium is very likely worth the upfront cost.