The Cast Boolits/Redneck Gold bar ingots (2 to 2.5 pounds) are stable sitting on the pot rim for preheating and several will go into the empty pot set end on. They also can be held with pliers or vice grips for easy lowering into the melt.
The mini loaf pan ingots (2.5 to 3 pounds) don't sit well on the rim, are harder to lower into the melt with vice grips or pliers, and will only go two or three into an empty pot.
It matters to me how well I can control adding ingots to a partly filled pot: sometimes a complete ingot will overfill the pot so being able to keep firm hold of what I don't want to drop into the melt as the submerged part liquifies is important. My ingots are stored in my unfinished basement and are exposed to moisture from the air and ground both, so preheating is to drive out any water as well as speeding melting with minimal temp drop.
The small loaf pan ingots (9 to 10 pounds) don't fit my casting pots at all, though they probably will go into a monster pot like the Magma. I cast those out of scrap for ease of storage and for batching and analysis.