It was almost a 50/50 split between the long and regular version of my separated beds when I took a poll earlier this year. I finally decided on a compromise. I'm going to make the regular size mattress and 2 frame sizes. You can then use the long sheets from my linen set to make it look like the mattress fills the long frame if that's what you want and fill it with pillows.
It's only a little more work this way and I thought it would be nice to have options. I have toddler beds to work on next.