The first question I'd ask is are you looking for a boarding solution or are you entertaining a rear deck? I'll assume since you included a liftgate solution that you are leaning in the direction of a deck-type solution?
Second question is if you intend to ever pull a trailer. If "yes", "maybe", or even "not sure" it leads down one path; if "no" it opens a number of very different options.
Third question is are you looking for an off-the-shelf solution or are you going to fab/build/have built something custom?
Climbing: IMO the OEM steps are incredibly solid and stable (and for climbing five feet into the upper atmosphere, stability is a good thing to have). So if you have the OEM steps, I'd certainly prefer them over the lighter-weight, folding solutions (I've yet to find one of those that I could jump up and down on that didn't have some level of play). You can march a herd of drunken tapdancing elephants up the OEM steps w/o flexing them. Also, IMO steps are far "more accessible" than ladders (old people like me are supposed to stay off ladders for a reason). The OEM steps can usually be had off GP for $100-200 plus shipping if you keep an eye out for them (or $1000-2000 from your friendly point-of-compass military surplus vendors....who get them from GP, etc).
Platform: If a trailer is never going to be in your future then a ridged solution is possible. Tons of great examples of this can be found (Keith's rig, Neil's rig, etc). If you intend to tow, then there are all sorts of folding read-deck options (and if you don't make the deck too deep, it can be lowered into place w/ having to unhitch a trailer) .
IMO, a liftgate solution for ingress/egress into a habitat isn't ideal unless you're in a disability situation (in which case even getting into the cab makes these trucks a questionable platform). While liftgates open up some carrying options (bikes, motorcycles, etc) you need to be well-thought-out in the planning (to me stowing stuff at the door is like folding beds, never in the position you want them when you need them, always needed to be rearranged and remade before you can go to sleep, in the way when you wake up). And again, if there is a trailer involved the trailer will need to be removed before the gate can be deployed.
There's no "wrong" answer, but it's all very situational IMO.
*since I have a M1083 trailer behind my M1079 and want to keep all my options open for future trailering of all sorts, a fold down rear deck is the direction I'm headed. To negate having to remove the trailer every time I want into the hab (major OEM design flaw, IMO), I'm keeping the deck at 4' deep so it can drop down over the tongue and not contact the trailer's box. I'll setup my OEM steps off the side for ingress/egress. Another benefit of a fold-up solution is that when the truck is not in use, it adds another security barrier to the habitat and it's contents.