Sandwich wall: building it "in place" or separatel

It seem some people build their sandwich wall (ply/stick & foam/ply) separately and when done mount it on the floor.
Others do it in place, as in they create the wall frame on the floor and then skin it, like here:
http://www.tnttt.com/viewtopic.php?t=17745&postdays=0&postorder=asc&start=45
I was gonna do it separate but because I'm lacking a large flat work surface and might have to handle the wall all on my own, it seem "in place" might be easier.
Any reason to prefer one over the other ?
The only minus i see with "in place" would be that it might be more difficult to apply pressure to the skin while the adhesive sets since it's vertical.
comments ?
Others do it in place, as in they create the wall frame on the floor and then skin it, like here:
http://www.tnttt.com/viewtopic.php?t=17745&postdays=0&postorder=asc&start=45
I was gonna do it separate but because I'm lacking a large flat work surface and might have to handle the wall all on my own, it seem "in place" might be easier.
Any reason to prefer one over the other ?
The only minus i see with "in place" would be that it might be more difficult to apply pressure to the skin while the adhesive sets since it's vertical.
comments ?