I would consider myself a less than experienced quilter, a bit over two years of sewing and a dominant hand with fingertips missing, so if I can do either...in this case both, almost anyone can. There are some obvious differences...Niemeyer is usually more geometric and less curvilinear ( until recently) and DeJonge's usually have a vast amount of circles and tight arcs that require a lot of matching. If you have done one of Judy's then you get just how critical it is to keep things organized, not confusing sew lines and a host of other more logical things you forget are essential...until you try of one their respective projects. They both have mistakes and have posted corrections that you likely need to hunt down, some older ones of JDJ lack papers, and Judy's have more specific directions but they can be a bit unclear at times...so pluses and minuses for both of them. I recently chose a Jacqueline DeJonge pattern called Curling Colours: it had a quadzillion triangular pieces, a ton of intersecting curves, made it into a king size and I still slogged through it...and you know how guys are about directions.
Sidebar: about two-thirds through this quilt top I found a method that uses freezer paper ...that is frequently referred to as "flip and sew" and that saved me from tearing away all those pesky pieces of paper. You can convert this technique to employ the papers provided and a re-positional glue stick from an office supply store.
I recently posted all the advantages of this method on this board elsewhere... if this is of interest? I also started to employ glue basting, clipping curves and a bunch of cool techniques that I learned from a Craftsy course...that you more experienced quilters likely know, but that also improved my final product.
So the bottom line? They both are not a cake walk, you have to think and not get ahead of yourself...but they each have a distinctive look to their work and that is what either draws us to one or the other...or in my case...both. If you flip a coin you will likely be happy with the results with either of them and if you need more information to fill in the blanks any further...you can drop me a private message, but of you belong to a group that does paper piecing you are likely light years ahead of me.