ANH X-wing Luke is all Death Star trench battle and not much else (eg, no lightsaber). Great figure and hugely pivotal moment, but it is restricted to that film.
Anything ESB starts to encompass what Luke was and will be (within the OT), all outfits have both the blaster and lightsaber. It also means from a practical sense that he's all decked out. On the shelf both are eye catchers, the ANH trench scene wins on emotional beats while the Hoth battle wins on pure Star Wars fun.
Most iconic outfit from ESB is a bit tough too, I think the Bespin outfit is kinda boring (but it's the outfit he battles Vader in and yadda yadda), and Hoth is cool but a pretty brief scene in the end. So the Snowspeeder Luke could be a bridge in terms of figures on the shelf, if you're trying to avoid multiples from each film.