[Pitchwife]

[QUOTE=Rumil;591845]One thing that comes to mind is that Gimli was a Noble of a settled dwarven society, therefore expected to lead in the fighting, whereas Thorin and co., though descended from Nobility, aren't currently in charge of anyone much, so have no expectations of heroicism put upon them.
QUOTE]

If I remember correctly, Thorin was Durin's Heir, i.e. if not for Smaug, he would have been King under the Mountain (and if not for Durin's Bane, King of Khazad-dûm). As far as Dwarves are concerned, is doesn't get any nobler than that.
Gimli was descended from a junior branch of the same family, and he and Glóin his father lived with Thorin's lot before Erebor was resettled.
Thorin certainly put expectations of heroicism upon himself. The Quest of Erebor (UT) tells us that when he and Gandalf talked about dealing with Smaug, Thorin was all for war & battle, and Gandalf had a hard job convincing him of the burglary approach.