Vertical versus horizontal cucumbers

I have four cucumber plants in my garden this year. Two are in a raised bed, sprawling along the ground in a forgotten corner of our patio. Two have been trained vertically up the sunniest section of fence in my yard. Both receive the same amount of water and light, but the sprawling plants are well ahead of the vertical climbers. What gives?

The vertical climbers are lush with leaves and covered in yellow blossoms. I planted these seeds at the same time, but the horizontal sprawlers are now laden with cukes. A bit of (non-scientific) internet research confirms that vertically grown plants have lower yields. One source attributed this to increased water loss in vertically grown vegetables, but argues that while per-plant yield is lower, per-square foot yield comes out ahead. I guess what confuses me is that difference isn't in yields as much as it is in maturity -- -- the horizontal plants are in some kind of two week time warp ahead of the verticals. Is it because the verticals have to put more energy into growing up rather than sideways?

I am in no hurry for the vertical cukes to start producing, because we can barely keep up with what we have. We have already had to compost a few behemoths that were uncovered well past their prime -- and here I thought that only happened with zucchini! I am planning on pickling the smallest cucumbers as cornichons this weekend. We are having Greek salad for every lunch -- yes, life could be worse. The lesson in all of this is the usual one for me: next year, fewer plants will do.