For a single pan either will work good and drawing near the door OK.
Evaporators with a flue pan and a syrup pan, on most newer evaporators try to draw off at the back of the syrup pan, where the heat is more constant. Personally I prefer cross flow over lengthwise flow, especially if you draw at the back. Most of the issue is with lengthwise channels, the outside channel, where you have your draw off is not as hot because the sides overlap onto the edge iron of the arch.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.