Very interesting Dennis, i was installing a second Battery this week in my
T.Red van and i asked myself which one i should put there... (me who have
installed so many second Battery...ironic) 6-pack gel cell/depp cycle or normal.

In the pass years, i was driving a Bus, no fridge so i use to carry a
Koolatron 12V fridge, the need for a Deep Cycle was a must as hi often let
the fridge work overnight (over 40 hours at 3.5 amp on the biggest DC bat. i
could fit in the rear of the bus), that said, those battery (if not
carefully re-charged on a Deep Cycle charger once in a wile) were degrading
fast... not keeping charge that long, not getting fully charge...

Anyway, as i was testing my Dometic on propane this week with great success
(-4C/25F) i decided to fit a normal Battery (for now!) as i would not need
so much the koolatron anymore (great fridge by the way), only use the second
battery for LED light, radio and some computer work... and the PROPEX
heating system (GREAT heating system, i'm very impress!!!).

As the van was empty to a shell, it was easy to pass a main + wire
everywhere in the van to hooked every 12V accessories to the second Battery.
When the ignition switch is closed, both battery are separated from each
other by a main realy.

My conclusion is if normal battery don't go too low, they will stay tip top.
I often went very low with Deep Cycle one because of my Koolatron, but i had
to charge them fast as soon as they where too low. For my next Mexico trip i
intend to add a third gel cell battery (yellow top)under the rear bench as
those one can be left almost empty for a wile, sadly, they don't have many amps!

What i suggest you talk about is "how low can you go" and for how long, for
each kind of battery...

Conclusion #2
in the shop, i have many battery, all 3 kind, my yellow top was left unused
for amost a year, i charge this one back this week and it went full charge,
the DC one didn't do so well, unable to fully recharge this one... normal
battery are always kept fully charge on a wood shelf, so i don't know about
those going too low!!!

Cheers, Ben