The negatrans is just a very convenient glassless 35mm carrier. A glass carrier will hold the film flatter, but the difference may or may not be important depending on the size of enlargement and how critical you are. The compromise I use is an anti-newton glass upper plate and a standard glassless lower plate, since the natural curve of the film will hold it flat against the upper plate. (I use Durst, which makes it easy to mix and match carrier plates.)