a refractor has no obstacles in the image path which can cause diffraction. reflectors have "spiders" (Newtonians) and/or multiple optical elements which result in diffraction and lower respective image quality. both types have their advantages and disadvantages.
given any specific objective size, the refractor design is generally more expensive, and at a certain point (about 40"), refractors become infeasible due to the weight of the primary objective lens and the length of the tube. reflectors can, these days, be built to any dimension via multiple objective mirrors all controlled by computer to perfect alignment (well, within a reasonable degree of accuracy at least).
refractors are generally considered to be the instrument of choice for planetary viewing due to the pureness of the image path. reflectors are the instrument of choice for deep space and wide field viewing, due to the affordability of superior light gathering power of large mirrors vs smaller objective lenses for a given cost. a large folded reflector is far more portable than a large refractor, as well as more affordable.
so a determination of "which is better?" becomes dependent on what type of viewing you wish to do, how portable the system needs to be, and what your budget is.