The debate in touring circles as to whether panniers or a cargo trailer are the way to go is old, and I bring nothing fresh to either side of the argument.  I have, and use, both means of carrying the load.  Which one I choose is dependent on circumstances.

For road touring, where I'm riding my touring bike that's kitted out with front and rear racks, I prefer panniers.  But when I'm touring on the C&O Canal towpath, which has a packed dirt or crushed stone surface, I tend to prefer using my mountain bike.  As it has no provision for attaching racks or even the modern-fangled dry sack bags that mount on the forks, panniers are a non-starter and I'm left to fall back on my trusty old B.o.B Yak trailer.

Last weekend I did a two-night overnight ride while towing the trailer.  Packing is dead simple: heave everything into the dry bag, roll it closed and clip the ends down, toss it into the trailer frame, and away we go.

True, it's a bit less convenient to fish something out of it along the way.  True, it adds a third wheel (of a different size) to the rig, so I need to pack and carry a spare inner tube and tire that would otherwise be unneeded and stay at home on the workbench.  True, the trailer's a lot longer and more unwieldy than panniers when it's not actually in service.  It's harder to lug around and could pose difficulty if I were flying or trying to board a train, for instance, unless the train had space for checked luggage.

Yet for all that, it is (in my opinion) a great option in the right circumstances.

Even in inclement weather the contents of the dry bag remain safe and, well, dry.  As my panniers are not of the waterproof variety, this is in and of itself a huge virtue.

I don't care if the dry bag and / or trailer get a bit muddy and dirty: they're easily rinsed off and cleaned up, in a way that fabric panniers in particular are not. and they dry quickly.

When I'm parked up for the night the dry bag stays outside my tent.  The interior of the tent stays neater, because I use the dry bag for storage to keep all of the clutter contained.  Nothing gets left on the picnic table, so overnight dew doesn't create a soggy mess in the morning.

When riding the trailer tracks nicely and adds little by way of air resistance.  I've not tried it in a hefty crosswind but I'd wager a small amount of money that it's less affected, and has less overall effect on handling, than panniers would in a similar situation.  I've read numerous accounts of cyclists using panniers who've been blown sideways- either into the lane or off the road, depending on which way the wind's blowing, but I've never read similar stories from trailer users.  Perhaps that's simply a reflection of how many more pannier users there are than trailer-towers; I don't know.

It takes a long wall space to park the bike/trailer combination but so what?  I've never failed to find a suitable spot when I wanted one.  Plus, I can jackknife the trailer and use it as a "kickstand" of sorts: the trailer rests on one side and holds the bike itself more-or-less upright.  (That's a trick unique to the B.o.B Yak design, I think; it wouldn't work with a two-wheeled trailer and apparently doesn't work with some other one-wheel designs.)

Keith I’ve dabbled with a few different ways of carrying stuff on bikes, but I’ve never tempted to try a touring trailer of any description. If I had though, BOB would be my choice. They seem to have an excellent reputation.

From what I’ve read and heard, where trailers come into their own is on long tours through arid areas where a lot of water has to be carried. Having the weight off the bike’s frame and wheels is a big plus it seems.

Panniers have always served my touring needs and I never even considered a trailer until I got the idea of taking my dog, Diggity, on a tour with me.  I bought a Burley Bee for that purpose, because I couldn't imagine stuffing my 34-pound best friend in one of my panniers.

Unfortunately, after several local rides, I learned Diggity was definitely NOT a touring dog.  He's fine for about twenty minutes, but then he starts barking non-stop, and nothing will appease him--which is weird because I had previously taken him for rides in a basket strapped on top of my rear rack and he seemed to enjoy it for up to 15 miles. 

Maybe he didn't like being so close to the road in the trailer.  Maybe his age (13-years) is making him less adventurous.

Greg good point.  Touring with pets is an excellent example where a trailer is probably the best option. And thinking about it, touring with young children, a trailer would be hard to surpass. Preferably on traffic free trails; though I met a family in Taiwan who’d cycle-toured all the way there overland from Western Europe with young kids. 

BTW that’s a great name for your dog. Diggity. Fantastic. We have Jester the dog-pound rescue collie bitsa. He’s exhausting enough to travel with in a car. He’d be a total liability to himself, me and wider society if an attempt were made to contain him in bicycle trailer.

I loved the cruising down the road part of touring with a trailer. All of my stuff was somewhere in that one bag. I used the BOB for several years. Then the inconvenience of finding a parking spot for that long rig won out and I went to panniers. I still have the BOB, although it hasn't seen the road in a number of years. 

We still have a BOB hanging in the bike room downstairs, waiting for the next time we go on a camping tour. We may need the BOB in order to pack along all the gear we require on a tandem bike.  At our age, our medications and assorted medical paraphernalia alone take a disconcerting amount of space. As younger riders we towed the BOB along with four panniers and a loaded rear rack on our Canondale tandem on the northern part of the Adventure Cycling Continental Divide route.  It worked surprisingly well with the biggest hurdle being having to disconnect the trailer and take of the panniers so that we could carry the tandem across the many stream crossings.  Last summer, as a test, we camped out with the tandem one night just to see if we could get all of our required camping gear on the tandem without using the BOB.  We made it, but just barely.  If we had been packing food and water and more cold weather clothing we would still need the BOB.  

I, too, have enjoyed some tours with a BOB Trailer. The most recent was in southern Ontario in 2021. You mention jack-knifing the trailer as a way to stand the bike. Though I never experienced a problem, I have read that this puts a lot of torque on the bike and can cause issues. When I read that, I added a kickstand to my BOB, and find it works beautifully.