I thought I would do a test of 3 different mantles on 3 as near as possible identical lamps. All three lamps are Petromax 500 HK. Two are Bundeswehr 829B (made 1969 and 1962) and the one in the middle is a modern 829.
All 3 using identical paraffin (from a UK hardware store, B&Q as it happens) and all operating at 2.5 Bar. After lighting they were allowed to settle down for 10 minutes before taking pictures. I stopped down the aperture of the camera to try to show the mantles properly as otherwise the pictures were just a white out.
The surprise is that there seems very little between the mantles. They are all so bright there is not much in it, either to the eye or to the camera. According to my geiger counter, the Peerless mantles are radioactive but the Coleman is not so it does not seem to follow that thorium mantles are always brighter.
From the stopped down picture it appears that the brightest is the Peerless 24A and the dimmest the Peerless 111.
Of course, these results only apply in these specific circumstances and they may perform very differently on different lamps.
Anyway, I hope you like the pictures. It was fun but I nearly blinded myself!
From left to right:
1) Peerless 111
2) Peerless 24A
3) Coleman Gold Top 1111