I would definitely recommend using a rear rack vs a trailer. Quite often wheels on road bikes are not as strong as on touring bikes made for added loads/weight. Over the past couple of years, I have a had couple of customers arrive at the shop while on a tour. Both were riding road bikes with trailers, and both had broken several spokes. To give you some history, both bikes were only a couple of years old, one rode by a man about 180 pounds and one by a woman who weighed 140.... both were carrying loads that were about 40 pounds.(front and rear combined) And these are only the most frequent bikes that I've seen, defintely have seen lots more over the years.

On a touring bike, you can choose to use either, but on a road bike I truly think that you are safer with a rear rack.

At any rate, it's your decision to make. Have fun and enjoy your adventure !