In 1996 Mac users were far more familiar with BeOS than NeXTSTEP. Even though it was a developer release, Be was marketing heavily to Mac users (like giving away free CDs) and BeOS could run on Macs so Mac users could try it side-by-side with MacOS and form firsthand impressions. (I was triple-booting MacOS, BeOS, and Linux on my Power Mac with a bunch of Jaz carts.) Meanwhile NeXTSTEP was expensive and ran on expensive non-Mac hardware.

BeOS was also optimized (probably over-optimized) for first impressions; the immaturity and architectural mistakes were hidden behind a facade of "OMG it's so fast and pretty". The BeOS GUI with its cartoony 32x32 icons was also a lot closer to MacOS than NeXTSTEP with it's huge high-DPI GUI, so BeOS looked like "Mac done right" while NeXT was a foreign culture.

So yeah, NeXT was better but most Mac users had no way of knowing that at the time.