My new boat is around 2.5 tonne and has a mackay aluminium trailer with keel rollers and skids.
I was very dubious about not having full multi-roller but after launching and retreiving with the outer skids I'm very happy with the skids.
The obvious advantage is weight saving with no outer roller sets. At 3200kg on the trailer need every kg I can get...
The mackay ally trailer is nice bit of gear but expensive. Runs hydrastar electric brakes.
regards
Anthony