Drum brakes every time.
If you leave a trailer with disc brakes for more than a week or so the bloody brakes sieze on,they eat pads like there is no tomorrow and the discs tend to crack if your running at full weight.They are also more prone to brake fade.
Drums can absorb a lot more heat due to their size and you also have a much larger braking surface area. Maintainance is not really an issue as to change pads you have to ,in 99% of axles remove the wheels.With drums you just undo the hub nuts and pull the wheel ,brake drum and hub off as one assembly.To change the shoes takes about five minutes,repack the bearings and slide the hub assembly back on.Just chip the crud ring off around the edge of the drum and they slide on easy.
Can reline a tri axle BPW in about 3 hours.Just need a decent wheel dolly and maybe a good hub puller if the bearings fret to the axle lands.Just a ten minute bed in and your ready to go.Should last a good 80 to 100,000 km per reline.
Shoes are cheaper than pads and drums are cheaper than discs and calipers cost a bloody fortune.Just got to keep the camshaft bushes and slack adjusters greased and they last for years.If your going to wash and repack the inner bearing best to replace the hub seals but these are only a few quid.