From reasonably frequent observation flying CX
out of Sydney, the A330 climbs faster than the A343. For example, we usually seem to go straight to either 36,000 feet or 38,000 feet on departing Sydney on the former but in the low 30s for the latter, although it usually seems to reach 39,000 feet or more, I'm fairly certain I've seen 41,000 feet toward the end of the stage either way more than once.
The A346 is sometimes on the route. It went again to 36,000 or 38,000 feet straight off.
I've now flown the A345 with EK
several times to Auckland (before it was replaced by the 773) and to Dubai. The Tasman stage seemed to be at 40,000 feet both ways, certainly higher than is usual on the smaller jets. Going to Dubai out of both Melbourne and Sydney late at night we went straight to the mid 30s, I think 35,000 or 36,000 feet. However I haven't flown the route in reverse so I can't comment on departures from Dubai, other than to say going to Europe the 777s and A330s both went to the low 30s and stayed there, perhaps as much to do with ATC requirements as anything else, since you do notice a bit of traffic in that part of the world.
The highest altitude I've ever noticed on a commercial jet other than Concorde was something above 43,000 feet on a Qantas SP
a few hours out from Sydney coming in from the US.
However back in the days of Comet IV
services for BOAC out of Essendon Airport in Melbourne we'd get to 40,000 feet on the stage to Darwin routinely.
I think the windows on the old Comets will actually prove to have been bigger than anything we will see on a 787, but nowhere as interesting of course.