why are nuclear pores more prominent than membranous pores?

Answer 1

Nuclear pores are constructed of intricate protein structure called the nuclear pore complex (composed of many protein subunits, excellent engineering). The nuclear envelope is actually 2 membranes thick, and the nuclear pores traverse through the inner and outer membranes of the envelope and secured. As for membranous pores, I think you're referring to cell membrane pores/channels, which may be constructed of smaller protein structures and are therefore less prominent.