I really didn't like how the whip stitch turned out. Stitches were always visible. I did the ladder stitch for a while, but like you, found the stitching to be somewhat loose. It helped to tighten and knot the thread at every intersection.
My most recent "EPP" project, however, I did a little differently. I marked the seam lines on the back of the fabrics (very carefully and accurately
) and sewed them by machine. Because I had to take my time, stop sewing 1/4" from the edge instead of sewing off the edge, and be very careful to make sure points matched, etc, it wasn't any faster than sewing by hand. But I was pleased with the quality of the finished product.