is mdx stronger then ndx?

i have a customer support programme that use dbase for database. I used
to use ndx indexes for my dbf files but after, for electrical problems
(light off etc), i needed reindexing and i used dbiregenindex  to
regenerate mdx files. so I am now using MDX files to index. But i think
mdx are not stronger then ndx. Do you have any idea or experience about
this subject?