A taildragger is more suited to rough ground, from the standpoint that you can control the prop clearance to a greater degree than with tricycle gear..... but this depends a great deal on your skill level... tricycle gear can help keep the prop out of the dirt, but it can also dig in, if you get unlucky. <Kind of like a baseball infielder getting a "bad bounce.">
as long as you've mastered flying a taildragger, you'd probably find it easier to get it off a rough field than the same airplane with a tricycle layout.
and yes, almost any trainer can be modified to a taildragger....
specifically what trainer are we talking about?