Definitely do a forum search.
Trailers let you haul a lot of weight and volume. Like most things in life, this is both a pro and a con. It's a pro because you don't have to figure out how to lighten your load, and you can have lots of bibs and bobs for every contingency. It's a con because well... no one really wants to have to manhandle a 30lb bike, 30lb trailer and 100lbs of gear, especially when the trailer got a surprise flat. Trailers will usually work with most any bike. Again, both a pro and a con. If you have a much loved bike that you put 100+ miles on each week, rain or shine, a trailer can pair with your bike and let you take your best bud on tour. If you're new to biking or don't bike a lot, a trailer can also let you get way in over your head on a bike that fits badly and is causing injuries.
On my first tour, I used panniers. I had the option of using a trailer, since friends own a Burley Nomad and it was garaged in favor of their toddler's trailer. But... it was a short distance weekend tour, and I could easily fit my gear in one of my panniers, leaving the other one free. I also planned to ride mostly on state trails, so dirt roads for the whole route. Dirt roads are tougher to ride on, and adding a trailer's extra drag probably would not have been fun. The state trails are also pretty narrow, and I could easily imagine the trailer causing problems if the route was heavily traveled. And I'm used to my panniers. While I don't use them every single ride, I do put on a lot of loaded miles with them every week. By comparison I'd had maybe as much as 20 miles in total riding with the trailer when I left on my tour.
I don't think one method or the other is "best". And almost a year on? We've got a brand new Burley Nomad of our own, and we'll probably pick up a second set of panniers in the next few months for my partner to use. For touring, I can definitely see the merits of a single wheel trailer too. But left to myself, I'd probably pick my much loved panniers and my much loved bike for my next tour... because I use them all the time and I know how they work and what my limits are with them.