Compared to a disc alone, the efficency is about 30-50% higher, meaning you use less to achieve the same ppm's/effect on plants.
Also, the evenness and response time to go from 3-4ppm of CO2 at night to the day when you need CO2 is reduced by 80-90% in that first 1 hour or so.
These are things few aquarist measure or consider.
But.......they both work as methods for adding CO2......and you use more CO2, which is no big deal really, it's cheap.
What is a bigger deal, at least to me, is the response time, evenness, and consistency of the method. It needs to be able to produce good stable rapid influx of CO2 and keep it there.
The less I have to mess with CO2, and have it keep rising later after I set it at a particular rate, the less chance I will add too much and gas the fish/add too much CO2.
The CO2 becomes easier to manage and adjust.
Disc are always clogging and need cleaning, if you miss doing that, the aquarium gets poorer growth, algae etc.
I've go the routine down for keeping disc clean, but it'd be nice not to bother with that, make adding CO2 to a good level with less fish issues. the mazzei and the Needle wheel offer that much better than disc, particularly when higher light is used or higher fish loads, more sensitive fish.
There are trade offs, but they tend/can be reduced and pretty much a non issue if you can easily DIY the needle wheel. Mazzei's require a lot more pressure to strip the gas into a mist making them good for larger systems and bad for smaller aquariums.