For kids or luggage?
If for kids, then I can recommend a Croozer.
It is jolly well built, rolls nicely, not too ridiculously heavy, tons of space for luggage (I’ve camped with a baby and all our camping gear in the back of it), and only quite expensive, as opposed to the ridiculously expensive Chariot ones. Oh and it can be a running buggy or a normal (if large) round the shops buggy, it comes with the different wheels etc.
All the hire places round us have Burley ones. Personally I don’t think they’re as cozy as the Croozer, but I presume they are also quite robust.
Cheaper trailers I’ve seen are silly heavy, and have much less nice seats and less good straps etc. for holding the kids in, which I think probably makes a difference.
I have a double, which is okay, but a bit wide sometimes, particularly off road – a single trailer would be much better for when things get tight.
The seats on the Croozer are kind of hammocky – they hang off the frame, which gives the whole thing a bit of suspension – I’ve certainly never worried about not having the full on suspension of a Chariot trailer. Especially now Rose is two and she’s always egging me on to ride faster at speed bumps or little jumps on the track so she bounces in the air!