[Patashu]

you want a difficulty that brings out all the unique qualities of the song that you're stepping, however hard that needs to be to do it. If it's under a VD oh well, if it's significantly hard (FGO or higher) add in a simplified difficulty as well. if you've brought out as much as you can of the song and it's still not interesting or stands out from the litter don't send it otherwise send it
by 'bringing out unique qualities' I mean stepping whatever is the most interesting at any given point in time. if something new comes in and it's a cool rhythm you should change your patterns around to account for it. do this as much and as consistently as possible and you step file good.

spread biased and all it entails (pitch relevant techniques, pattern relevancy, no worries for 'flow' issues that an index or one-hand biased file might have) is probably the way to go.
(if you still have no idea what the **** watch some IIDX videos or play random files from the dark chancellor pack/vgmp3)