I guess it depends on where you live and what your access is to a ski shop.
** IMPORTANT DISCLAIMER: There is a difference between a ski gear 'shop' and a ski gear 'store'.
If you live in, UT, CO, CA, or the Northern half of VT, you can find a business known as a ski 'shop', with a fitter that actually knows what he/she is doing. You will most likely be better off going to the fitter to get a proper shell fit and get to try a selection of various brands and models. You may luck out and get the just-right boot from the internet but its a crap shoot and you may find yourself buying new boots every season.
Now, if you live elsehwere and cannot get to one of the 'ski shops' noted above, you might as well just buy online as, with a few exceptions, ski 'stores' in the Midwest (!! DANGER WILL ROBINSON !!) don't have the slightest clue as to what makes a good boot-fit, let alone possess a rudimentary understanding of the products they sell. You will probably have just as much luck buying online -- or going into the 'ski stores' to try on the boots yourself, decide what fits, and purchase them online. WIth but a few exceptions, you will not find any meaningful or valid information on what makes a proper bootfit from the Midwestern 'ski store.' In many cases you may actually find you did a better job of selecting the right boot for your foot than what was handed to you by the high-school sales rep working in the 'ski store.'