i would classify a hybrid as being a battery that can do deep cycle and also do starting duty, but neither really well
marine batteries fit that category,
i would expect a starting battery to maybe put up with a couple dozen deep discharges before it gave up, and that only if you recharge immediately after doing the deed.
i would expect a hybrid (marine) battery to do maybe 100-200 cycles to 80% depth of discharge before it died. and i would not expect more than maybe 3 years in starter duty if it is doing so in cold climates. this too only if it is recharged immediately after such use.
i would classify a golf cart battery as an entry level deep cycle battery, and expect around 4-500 deep cycles (80%DOD) before end of life, and only if it was recharged immediately after each cycle.
one could probably do a bit better with the hybrids "if" the cycles were shallow and recharge done immediately, but it is doubtful that they would ever make more than maybe 250 such cycles, in my opinion.
i think a golf cart deep cycle might well make maybe 800 or more cycles if short/shallow cycled and well maintained, but i would not count of more than 500 cycles and then if it got more i would be pleasantly surprised.
btw, i too figured to buy the best i could afford figuring it would work out lower cost over the lifespan of the batteries, however i had to give this another "thunk" after doing the analysis.
then things changed for me, that is my needs for a battery bank changed
i now have sufficient solar pv to cover my loads, and i can schedule those loads for the most part to be serviced during the daylight hours.
so my needs for a battery bank are more for a buffer than for bulk storage.
development of a trigenerator (combine power/heat/cooling) provides me the ability to maintain a battery bank whether the sun is shining or not, so again my needs for a battery are more as a buffer
what i am now seriously considering is the use of automotive starting batteries, because my needs are for a buffer (which any battery can provide) and i can schedule my loads, and my need for the bank to cover a load is not much over 30 seconds before the trigen can start, come on line and take over powering the loads that the solar either can't or if the sun isn't shining.
a 30 second draw is well within the design parameters of an automotive starting battery. such a battery is really good at doing a couple things, that is providing a lot of amps over a short period of time, ability to accept a high rate charge, and because of economies of scale and fierce competition they are about as cheap a battery as one is likely to find... and their lifespan is reasonable given a very shallow cycle of less than 10% of capacity. my thinking is if i can size the battery bank so that the 30 second draw is around 5% of capacity the bank likely would have a lifespan of 5 years or more.
another thought while on this tangeant
my inverter bank will provide 2.2 times it rated power as surge capacity, this allows me to start a much larger motor load with a smaller generating capacity on its own, and powered by a bank of automotive batteries the ability to provide a huge surge without damage to the batteries is something to consider.
getting back to economies of scale, lets take a look at the trucking industry. for whatever reason truck parts are far better priced than car parts any day of the week. batteries are no exception.
i can find a dealer any given month that will have for instance 950cca 12volt batteries for less than a hundred bucks a copy, and they come with a good warrantee, some of which will give you replacement for the first 2 years and prorate another 3-5 years. of course they don't know what i plan for them, nor am i going to tell them either. i keep the receipt and take them home, should they fail i bring them back and get replacement or adjustment/replacement.
admittedly this sort of battery is of little use to anyone wanting a storage battery and to deep cycle it. it likely would not make more than 20-30 deep discharges before being toast. warrantee or no warrantee that sort of lifespan is no good under that sort of service.
fwiw
bob g