Printers pallets are generally better quality, because they carry a bloody great stack of SRA2, SRA1 or SRA0 paper, which is strapped down with chipboard sheets on the top to keep it perfectly flat, IIRC the SRA2 pallets are 960×720, or thereabouts. I used to run a folding machine which needed a work surface at either end for knocking-up the paper to get it even and get some air into the sheets for folding, and at the other end for bundling and putting into plastic mail tubs, and I built two out of seven pallets stacked on top of each other, strapped together, then a sheet of the chipboard hot-glued on top. Nice and firm and stable, the gaps inside the pallets made very useful storage spaces as well, thinking about it they were solid enough you could bolt a vice onto the top, and probably a belt sander – if I needed to move them I had to use a pallet truck.
We did get really big ones in as well, usually painted blue, and very, very heavy! I think they carried the plastic mail tubs we used for sending the finished mail to the Post Office sorting office along the road.