Calum Douglas stated that the Jumo 213J would have probably been the best piston engine of the war. Coming from such an expert where does that leave the Sabre? Figures I've seen for both seem to favor the Napier product though , as you said.Sabre was more modern, not that that was automatic win for it (it probably gave a lot of trouble for being very modern engine), while Jumo 213 was very 'classic' engine pushed to the limit.
Sabre also have had more potential, the margin might be not that great, though.
Efficient - in sense of fuel mileage, or in sense that it excelled in it's job, or what one gave better bang for buck? Jumo 213 will be easier and cheaper to make, probably will have better mileage, however Sabre was making better power and was in service much easier, even if we remove the 1942, the year of Sabre's troubles.
Sabre was probably overall better, by virtue of serving much longer than the Jumo 213 while making better power.
Before people start yelling 'what about the 213E and F' - all good, but too late. The 213J was even a greater engine, but it missed usage in the ww2.
How do the power-to-weight-ratios of the two compare?The French version was advertised at 2300hp for take-off using 100/130 and water injection and 2100hp dry.
It also weighed 2100lbs. or about 400lbs less than the last Sabres. It was supposed to offer about 10% less fuel burn per hp (but a at a lower power rating) but some of the published fuel burns for several engines may be a bit off.
Sabre was flying dangerous missions during during the 3 years of war.Calum Douglas stated that the Jumo 213J would have probably been the best piston engine of the war. Coming from such an expert where does that leave the Sabre? Figures I've seen for both seem to favor the Napier product though , as you said.
The original question perhaps needs a little parsing. You either need to pick a point in time, and say on THIS date, which one was at a greater level of technological development and war potential, or, dispense with any semblance of history, and say, "here are both engines, new in boxes, unpack them and critique them today".