UF4004 vs. N4004

The UH400x range have a soft turn-off as well as being fast so they produce a lot less switching noise as a result of the 'snap' turn-off of the reverse currnet that flows for a short time when the diode gets reverse biased. On normal 50/60Hz ac supplies that effect is not normally a problem. (When you get up to SMPSU switching frequencies it is a very different matter!)